Antifungals — MCQs

Q: A 35-year-old African American male is admitted to the hospital following a recent diagnosis of systemic histoplasmosis and subsequently treated with an intravenous anti-fungal agent. During the course of his hospital stay, he complains of headaches. Work-up reveals hypotension, anemia, and elevated BUN and creatinine. His medication is known to cause these side-effects through its binding of cell membrane ergosterol. With which anti-fungal is he most likely being treated?

Amphotericin B. ***Amphotericin B*** - **Amphotericin B** is known for its significant side effects, including **nephrotoxicity** (leading to elevated BUN and creatinine, and potentially anemia due to reduced erythropoietin production) and **infusion-related reactions** like headache and hypotension. - It works by binding to **ergosterol** in fungal cell membranes, forming pores that lead to cell death, but it can also bind to cholesterol in mammalian cell membranes contributing to its toxicity. *Griseofulvin* - **Griseofulvin** primarily acts by binding to **keratin** and interfering with fungal **mitosis**; it does not bind to ergosterol. - Its main side effects include **GI upset**, headache, and photosensitivity, but not prominent nephrotoxicity or hypotension in the manner described. *Flucytosine* - **Flucytosine** is an antimetabolite that is converted to **5-fluorouracil** within fungal cells, interfering with RNA and DNA synthesis. It does not bind to ergosterol. - Its major adverse effects include **bone marrow suppression** (leukopenia, thrombocytopenia) and liver enzyme elevation, not the constellation of symptoms (hypotension, renal failure) described. *Fluconazole* - **Fluconazole** is an azole antifungal that inhibits **ergosterol synthesis** by blocking fungal cytochrome P450 enzymes. It does not directly bind to ergosterol. - While it can cause some GI upset and liver enzyme elevation, it is generally well-tolerated and less associated with acute nephrotoxicity or hypotension compared to Amphotericin B. *Terbinafine* - **Terbinafine** inhibits **squalene epoxidase**, an enzyme involved in ergosterol synthesis, rather than binding directly to ergosterol itself. - Its main side effects include **GI disturbances**, headache, and liver enzyme abnormalities, but typically not the severe nephrotoxicity and hypotension associated with Amphotericin B.

Q: A 28-year-old woman with HIV comes to the physician because of an 8-day history of severe pain while swallowing. She has been hospitalized several times with opportunistic infections and has poor adherence to her antiretroviral drug regimen. Endoscopy shows extensive, white, plaque-like lesions in the proximal esophagus. Culture of a biopsy specimen grows Candida albicans. Treatment with intravenous anidulafungin is initiated. Which of the following is the primary mechanism of action of this drug?

Decreased glucan synthesis. ***Decreased glucan synthesis*** - **Anidulafungin** is an **echinocandin** antifungal drug that inhibits the synthesis of **β-(1,3)-D-glucan**, a crucial component of the fungal cell wall. - By disrupting the fungal cell wall, **anidulafungin** causes **osmotic instability** and ultimately leads to cell lysis and death, making it effective against *Candida* infections. *Binding to tubulin* - This is the mechanism of action of **griseofulvin**, an antifungal agent primarily used for dermatophyte infections. - **Griseofulvin** interferes with **microtubule formation**, thus inhibiting fungal mitosis. *Inhibition of squalene epoxidase* - This is the mechanism of action of **terbinafine**, an antifungal drug commonly used for dermatophyte infections like onychomycosis. - **Terbinafine** blocks the synthesis of **ergosterol**, an essential component of the fungal cell membrane, by inhibiting **squalene epoxidase**. *Decreased DNA synthesis* - This mechanism is associated with **flucytosine**, an antifungal agent that is converted to 5-fluorouracil inside fungal cells. - **Flucytosine** then inhibits fungal **DNA and RNA synthesis** and is often used in combination with amphotericin B for severe systemic candidiasis or cryptococcosis. *Binding to ergosterol* - This is the mechanism of action of **polyene antifungals** like **amphotericin B** and **nystatin**. - These drugs bind to **ergosterol** in the fungal cell membrane, forming pores that lead to leakage of intracellular contents and cell death.

Q: A 12-year-old girl is brought to the physician for a follow-up examination. Two months ago, she was diagnosed with asthma and treatment was begun with an albuterol inhaler as needed. Since then, she has had episodic chest tightness and cough 2–3 times per week. The cough is intermittent and nonproductive; it is worse at night. She has been otherwise healthy and takes no other medications. Her vital signs are within normal limits. Pulmonary examination shows mild expiratory wheezing of all lung fields. Spirometry shows an FEV1:FVC ratio of 81% and an FEV1 of 80% of predicted; FEV1 rises to 93% of predicted after administration of a short-acting bronchodilator. Treatment with low-dose inhaled beclomethasone is begun. The patient is at greatest risk for which of the following adverse effects?

Oropharyngeal candidiasis. ***Oropharyngeal candidiasis*** - **Inhaled corticosteroids** like beclomethasone can suppress the local immune response in the oral cavity and pharynx, leading to opportunistic fungal infections. - This condition, commonly known as **thrush**, presents as white patches on the tongue and oral mucosa, which can be mitigated by rinsing the mouth after inhaler use. *Hypoglycemia* - **Inhaled corticosteroids** typically have minimal systemic absorption at low doses and are not associated with hypoglycemia. - **Hypoglycemia** is more commonly associated with diabetes treatment or conditions affecting glucose regulation. *Easy bruisability* - While **systemic corticosteroids** can cause skin thinning and easy bruising with long-term use, **inhaled corticosteroids** at low doses have very limited systemic effects. - The risk of easy bruisability is extremely low with the prescribed treatment in this patient. *Bradycardia* - **Beta-agonists** (like albuterol) can cause tachycardia, but inhaled corticosteroids themselves do not significantly affect heart rate. - **Bradycardia** is not a characteristic adverse effect of beclomethasone; it is typically associated with certain cardiac conditions or medications like beta-blockers. *High-pitched voice* - **Inhaled corticosteroids** can sometimes lead to hoarseness or dysphonia due to local irritation or candidiasis of the vocal cords, but not specifically to a high-pitched voice. - A high-pitched voice is not a recognized adverse effect; rather, a change in voice quality such as hoarseness is more typical.

Q: A 45-year-old man presents to the emergency department with difficulties swallowing food. He states that he experiences pain when he attempts to swallow his medications or when he drinks water. He reveals that he was diagnosed with HIV infection five years ago. He asserts that he has been taking his antiretroviral regimen, including emtricitabine, rilpivirine, and tenofovir. His temperature is 98°F (37°C), blood pressure is 100/60 mmHg, pulse is 90/min, respirations are 22/min, and oxygen saturation is 99% on room air. His physical exam is notable for a clear oropharynx, no lymphadenopathy, and a normal cardiac and pulmonary exam. No rashes are noted throughout his body. His laboratory results are displayed below: Hemoglobin: 12 g/dL Hematocrit: 37 % Leukocyte count: 8,000/mm^3 with normal differential Platelet count: 160,000/mm^3 Serum: Na+: 138 mEq/L Cl-: 108 mEq/L K+: 3.5 mEq/L HCO3-: 26 mEq/L BUN: 35 mg/dL Glucose: 108 mg/dL Creatinine: 1.1 mg/dL CD4+ count: 90/mm^3 HIV viral load: 59,000 copies/mL What is the best next step in management?

Fluconazole. ***Fluconazole*** - The patient's **odynophagia**, low **CD4+ count**, and high **HIV viral load** are highly suggestive of **esophageal candidiasis**. - **Fluconazole** is the initial empiric treatment of choice for suspected esophageal candidiasis in HIV-positive patients, given its high efficacy and good tolerability. *Nystatin* - **Nystatin** is typically used for **oral candidiasis (thrush)**, which presents with white plaques in the mouth. - The patient has a **clear oropharynx** and **odynophagia**, indicating esophageal involvement, for which nystatin is less effective. *Oral swab and microscopy* - While an **oral swab** can confirm oral candidiasis, it is not sufficient for diagnosing **esophageal candidiasis**. - Given the patient's symptoms of odynophagia and high clinical suspicion in an immunocompromised patient, empiric treatment is preferred over initial diagnostic testing for uncomplicated esophageal candidiasis. *Methylprednisolone* - **Methylprednisolone** is a corticosteroid used to reduce inflammation and is not indicated for the treatment of **candidal infections**. - Using corticosteroids in an immunocompromised patient with an active opportunistic infection could worsen his condition. *Esophageal endoscopy and biopsy* - **Esophageal endoscopy and biopsy** are typically reserved for patients who **fail empiric antifungal therapy** or present with **atypical symptoms** not consistent with candidiasis. - Given the clear clinical picture, initial empiric treatment with fluconazole is the standard first step.

Q: A 45-year-old man comes to the physician because of a 3-day history of pain in his mouth and throat and difficulty swallowing. He has a history of COPD, for which he takes theophylline and inhaled budesonide-formoterol. Physical examination shows white patches on the tongue and buccal mucosa that can be scraped off easily. Appropriate pharmacotherapy is initiated. One week later, he returns because of nausea, palpitations, and anxiety. His pulse is 110/min and regular. Physical examination shows a tremor in both hands. Which of the following drugs was most likely prescribed?

Fluconazole. ***Fluconazole*** - Fluconazole is a potent **CYP450 inhibitor**, specifically **CYP2C9 and CYP3A4**, which can significantly increase the levels of drugs metabolized by these enzymes, such as **theophylline**. - The patient's symptoms of nausea, palpitations, anxiety, tremor, and tachycardia are consistent with **theophylline toxicity**, which would be exacerbated by co-administration with fluconazole. *Amphotericin B* - Amphotericin B is a powerful antifungal, but its primary side effects include **nephrotoxicity**, **infusion-related reactions** (fever, chills, rigors), and **electrolyte disturbances**, not theophylline toxicity. - It is typically reserved for **severe systemic fungal infections** and is not a first-line treatment for uncomplicated **oral candidiasis**. *Griseofulvin* - Griseofulvin is used to treat **dermatophyte infections** (tinea infections) and is not active against *Candida*. - Its main side effects include **gastrointestinal upset**, **headache**, and **photosensitivity**, and it does not significantly interact with theophylline. *Terbinafine* - Terbinafine is an allylamine antifungal primarily used for **dermatophyte infections**, particularly **onychomycosis**, and is not effective for candidiasis. - While it can cause liver enzyme elevation, it does not typically lead to theophylline toxicity or the constellation of symptoms described. *Nystatin* - Nystatin is a **topical or oral non-absorbable antifungal** used for superficial candidal infections, including oral thrush. - It is not absorbed systemically, so it has **virtually no drug interactions** or systemic side effects, and therefore would not cause theophylline toxicity.

Q: A 57-year-old woman with non-small cell lung cancer comes to the physician 4 weeks after her tumor was resected. She takes no medications. The physician starts her on a treatment regimen that includes vinblastine. This treatment puts the patient at highest risk for which of the following?

Invasive fungal infection. ***Invasive fungal infection*** - Vinblastine is an **antimitotic chemotherapy agent** that, like other chemotherapeutic agents, can cause **myelosuppression**. - **Myelosuppression** (particularly **neutropenia**) severely compromises the immune system, making patients highly susceptible to **opportunistic infections**, including invasive fungal infections. *Pulmonary embolism* - While cancer itself is a risk factor for **venous thromboembolism**, including pulmonary embolism, vinblastine itself **does not directly increase the risk** more than other chemotherapy agents. - The highest risk with vinblastine specifically relates to its impact on bone marrow. *Progressive multifocal leukoencephalopathy* - This is a rare, severe opportunistic infection of the brain caused by the **JC virus**, primarily seen in patients with **severe immunosuppression**, such as those with HIV/AIDS or on chronic immunosuppressive therapy (e.g., natalizumab). - While chemotherapy can cause immunosuppression, PML is not the most common or highest specific risk directly associated with vinblastine or its immediate, acute side effects compared to myelosuppression and opportunistic infections. *Pulmonary fibrosis* - **Pulmonary fibrosis** is a known side effect of certain chemotherapeutic agents like **bleomycin** and **busulfan**, but it is **not a primary or common adverse effect of vinblastine**. - The side effect profile of vinblastine primarily involves myelosuppression, neurotoxicity, and gastrointestinal effects. *Heart failure* - **Cardiotoxicity leading to heart failure** is a significant concern with certain chemotherapy drugs, particularly **anthracyclines** (e.g., doxorubicin) and some tyrosine kinase inhibitors. - **Vinblastine is not typically associated with cardiotoxicity or heart failure** as a primary or high-risk adverse effect.

Q: A 46-year-old man with HIV infection comes to the physician because of a 1-week history of severe retrosternal pain while swallowing. He has not been compliant with his antiretroviral drug regimen. His CD4+ T-lymphocyte count is 98/mm3 (N ≥ 500). Endoscopy shows white plaques in the esophagus. The most appropriate immediate treatment is a drug that inhibits which of the following enzymes?

Cytochrome p450 enzymes. ***Cytochrome P450 enzymes*** - The patient's symptoms (retrosternal pain on swallowing, white plaques on endoscopy) and severely low **CD4+ count (98/mm³)** are highly suggestive of **esophageal candidiasis**, a common opportunistic infection in AIDS. - **Fluconazole**, an azole antifungal, is the **first-line treatment** for esophageal candidiasis and works by inhibiting **14α-demethylase (lanosterol demethylase)**, a fungal **cytochrome P450 enzyme**. - This inhibition prevents the conversion of lanosterol to ergosterol, disrupting **fungal cell membrane synthesis** and leading to fungal cell death. *Squalene epoxidase* - **Terbinafine** and **naftifine** (allylamine antifungals) inhibit squalene epoxidase in the ergosterol synthesis pathway. - These agents are primarily used for **dermatophyte infections** (onychomycosis, tinea) and have **poor activity against Candida species**. - They are not appropriate for treating esophageal candidiasis. *DNA polymerase* - Inhibitors of **DNA polymerase**, such as acyclovir or ganciclovir, are used to treat **herpesvirus infections** (HSV, CMV). - While herpes esophagitis can occur in immunocompromised patients, it typically presents with **punched-out ulcers**, not white plaques. *Hydrogen-potassium ATPase* - **Proton pump inhibitors** (PPIs) target hydrogen-potassium ATPase in gastric parietal cells to reduce **acid secretion**. - These are used to treat **GERD** or **peptic ulcers**, which do not present with white plaques on endoscopy. - While PPIs may provide symptomatic relief, they do not treat the underlying fungal infection. *Phospholipase A2* - Phospholipase A2 inhibitors are used as **anti-inflammatory agents**, as PLA2 releases arachidonic acid, a precursor to inflammatory mediators. - These drugs have no role in treating fungal infections like esophageal candidiasis.

Q: A 69-year-old man with metastatic colon cancer is brought to the emergency department because of shortness of breath, fever, chills, and a productive cough with streaks of blood for the past 5 days. He has a history of emphysema. The patient does not have abdominal pain or headache. He receives chemotherapy with 5-fluorouracil, leucovorin, and oxaliplatin every 6 weeks; his last cycle was 3 weeks ago. His temperature is 38.3°C (101°F), pulse is 112/min, and blood pressure is 100/70 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 83%. A few scattered inspiratory crackles are heard over the right lung. His mucous membranes are dry. Cardiac examination is normal. Laboratory studies show: Hemoglobin 9.3 mg/dL Leukocyte count 700/mm3 Segmented neutrophils 68% Lymphocytes 25% Eosinophils 4% Monocytes 3% Platelet count 104,000/mm3 Serum Glucose 75 mg/dL Urea nitrogen 41 mg/dL Creatinine 2.1 mg/dL Galactomannan antigen Positive Which of the following is the most appropriate initial pharmacotherapy?

Voriconazole. ***Voriconazole*** - The patient has **neutropenic fever** (leukocyte count 700/mm3, recent chemotherapy) with pulmonary symptoms and a positive **galactomannan antigen**, which is highly suggestive of **invasive aspergillosis**. - **Voriconazole** is the recommended first-line agent for the treatment of **invasive aspergillosis**. *Ceftriaxone and azithromycin* - This combination is typically used for **community-acquired pneumonia**, targeting common bacterial pathogens like *Streptococcus pneumoniae* and atypical bacteria. - It does not cover **fungal infections** like aspergillosis, nor does it provide broad-spectrum gram-negative coverage suitable for neutropenic fever. *Rifampin, isoniazid, pyrazinamide, and ethambutol* - This four-drug regimen is the standard treatment for **active tuberculosis**. - There is no clinical or laboratory evidence (e.g., acid-fast bacilli smear, cultures) to suggest tuberculosis in this patient. *Ceftazidime and levofloxacin* - **Ceftazidime** is a third-generation cephalosporin with good gram-negative coverage, including *Pseudomonas*, which might be considered in neutropenic fever. However, it lacks adequate gram-positive coverage. - **Levofloxacin** is a fluoroquinolone that provides broad-spectrum coverage, but this combination still misses the likely fungal pathogen and is not ideal for initial empiric therapy in severe neutropenic fever. *Piperacillin-tazobactam* - **Piperacillin-tazobactam** is a broad-spectrum antibiotic with good coverage against both gram-positive and gram-negative bacteria, including *Pseudomonas aeruginosa*, making it a common choice for **empiric therapy in neutropenic fever**. - However, it does not cover **fungal infections**, which are strongly indicated by the positive **galactomannan antigen** in this immunocompromised patient.

A 35-year-old African American male is admitted to the hospital following a recent diagnosis of systemic histoplasmosis and subsequently treated with an intravenous anti-fungal agent. During the course of his hospital stay, he complains of headaches. Work-up reveals hypotension, anemia, and elevated BUN and creatinine. His medication is known to cause these side-effects through its binding of cell membrane ergosterol. With which anti-fungal is he most likely being treated?

A 28-year-old woman with HIV comes to the physician because of an 8-day history of severe pain while swallowing. She has been hospitalized several times with opportunistic infections and has poor adherence to her antiretroviral drug regimen. Endoscopy shows extensive, white, plaque-like lesions in the proximal esophagus. Culture of a biopsy specimen grows Candida albicans. Treatment with intravenous anidulafungin is initiated. Which of the following is the primary mechanism of action of this drug?

A 12-year-old girl is brought to the physician for a follow-up examination. Two months ago, she was diagnosed with asthma and treatment was begun with an albuterol inhaler as needed. Since then, she has had episodic chest tightness and cough 2–3 times per week. The cough is intermittent and nonproductive; it is worse at night. She has been otherwise healthy and takes no other medications. Her vital signs are within normal limits. Pulmonary examination shows mild expiratory wheezing of all lung fields. Spirometry shows an FEV1:FVC ratio of 81% and an FEV1 of 80% of predicted; FEV1 rises to 93% of predicted after administration of a short-acting bronchodilator. Treatment with low-dose inhaled beclomethasone is begun. The patient is at greatest risk for which of the following adverse effects?

A 45-year-old man presents to the emergency department with difficulties swallowing food. He states that he experiences pain when he attempts to swallow his medications or when he drinks water. He reveals that he was diagnosed with HIV infection five years ago. He asserts that he has been taking his antiretroviral regimen, including emtricitabine, rilpivirine, and tenofovir. His temperature is 98°F (37°C), blood pressure is 100/60 mmHg, pulse is 90/min, respirations are 22/min, and oxygen saturation is 99% on room air. His physical exam is notable for a clear oropharynx, no lymphadenopathy, and a normal cardiac and pulmonary exam. No rashes are noted throughout his body. His laboratory results are displayed below: Hemoglobin: 12 g/dL Hematocrit: 37 % Leukocyte count: 8,000/mm^3 with normal differential Platelet count: 160,000/mm^3 Serum: Na+: 138 mEq/L Cl-: 108 mEq/L K+: 3.5 mEq/L HCO3-: 26 mEq/L BUN: 35 mg/dL Glucose: 108 mg/dL Creatinine: 1.1 mg/dL CD4+ count: 90/mm^3 HIV viral load: 59,000 copies/mL What is the best next step in management?

A 45-year-old man comes to the physician because of a 3-day history of pain in his mouth and throat and difficulty swallowing. He has a history of COPD, for which he takes theophylline and inhaled budesonide-formoterol. Physical examination shows white patches on the tongue and buccal mucosa that can be scraped off easily. Appropriate pharmacotherapy is initiated. One week later, he returns because of nausea, palpitations, and anxiety. His pulse is 110/min and regular. Physical examination shows a tremor in both hands. Which of the following drugs was most likely prescribed?

A 74-year-old man is admitted to the medical ward after he developed a fungal infection. He has aplastic anemia. The most recent absolute neutrophil count was 450/µL. An anti-fungal agent is administered that inhibits the fungal enzyme, (1→3)-β-D-glucan synthase, and thereby disrupts the integrity of the fungal cell wall. He responds well to the treatment. Although amphotericin B is more efficacious for his condition, it was not used because of the side effect profile. What was the most likely infection?

A 57-year-old woman with non-small cell lung cancer comes to the physician 4 weeks after her tumor was resected. She takes no medications. The physician starts her on a treatment regimen that includes vinblastine. This treatment puts the patient at highest risk for which of the following?

A 46-year-old man with HIV infection comes to the physician because of a 1-week history of severe retrosternal pain while swallowing. He has not been compliant with his antiretroviral drug regimen. His CD4+ T-lymphocyte count is 98/mm3 (N ≥ 500). Endoscopy shows white plaques in the esophagus. The most appropriate immediate treatment is a drug that inhibits which of the following enzymes?

A 69-year-old man with metastatic colon cancer is brought to the emergency department because of shortness of breath, fever, chills, and a productive cough with streaks of blood for the past 5 days. He has a history of emphysema. The patient does not have abdominal pain or headache. He receives chemotherapy with 5-fluorouracil, leucovorin, and oxaliplatin every 6 weeks; his last cycle was 3 weeks ago. His temperature is 38.3°C (101°F), pulse is 112/min, and blood pressure is 100/70 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 83%. A few scattered inspiratory crackles are heard over the right lung. His mucous membranes are dry. Cardiac examination is normal. Laboratory studies show: Hemoglobin 9.3 mg/dL Leukocyte count 700/mm3 Segmented neutrophils 68% Lymphocytes 25% Eosinophils 4% Monocytes 3% Platelet count 104,000/mm3 Serum Glucose 75 mg/dL Urea nitrogen 41 mg/dL Creatinine 2.1 mg/dL Galactomannan antigen Positive Which of the following is the most appropriate initial pharmacotherapy?

Q10

A 45-year-old HIV-positive male presents to his primary care physician complaining of decreased libido. He reports that he has been unable to maintain an erection for the past two weeks. He has never encountered this problem before. He was hospitalized four weeks ago for cryptococcal meningitis and has been on long-term antifungal therapy since then. His CD4 count is 400 cells/mm^3 and viral load is 5,000 copies/ml. He was previously non-compliant with HAART but since his recent infection, he has been more consistent with its use. His past medical history is also notable for hypertension, major depressive disorder, and alcohol abuse. He takes lisinopril and sertraline. His temperature is 98.6°F (37°C), blood pressure is 120/85 mmHg, pulse is 80/min, and respirations are 18/min. The physician advises the patient that side effects like decreased libido may manifest due to a drug with which of the following mechanisms of action?

Antifungals US Medical PG Practice Questions and MCQs

Question 1: A 35-year-old African American male is admitted to the hospital following a recent diagnosis of systemic histoplasmosis and subsequently treated with an intravenous anti-fungal agent. During the course of his hospital stay, he complains of headaches. Work-up reveals hypotension, anemia, and elevated BUN and creatinine. His medication is known to cause these side-effects through its binding of cell membrane ergosterol. With which anti-fungal is he most likely being treated?

A. Griseofulvin
B. Amphotericin B (Correct Answer)
C. Flucytosine
D. Fluconazole
E. Terbinafine

Explanation: ***Amphotericin B*** - **Amphotericin B** is known for its significant side effects, including **nephrotoxicity** (leading to elevated BUN and creatinine, and potentially anemia due to reduced erythropoietin production) and **infusion-related reactions** like headache and hypotension. - It works by binding to **ergosterol** in fungal cell membranes, forming pores that lead to cell death, but it can also bind to cholesterol in mammalian cell membranes contributing to its toxicity. *Griseofulvin* - **Griseofulvin** primarily acts by binding to **keratin** and interfering with fungal **mitosis**; it does not bind to ergosterol. - Its main side effects include **GI upset**, headache, and photosensitivity, but not prominent nephrotoxicity or hypotension in the manner described. *Flucytosine* - **Flucytosine** is an antimetabolite that is converted to **5-fluorouracil** within fungal cells, interfering with RNA and DNA synthesis. It does not bind to ergosterol. - Its major adverse effects include **bone marrow suppression** (leukopenia, thrombocytopenia) and liver enzyme elevation, not the constellation of symptoms (hypotension, renal failure) described. *Fluconazole* - **Fluconazole** is an azole antifungal that inhibits **ergosterol synthesis** by blocking fungal cytochrome P450 enzymes. It does not directly bind to ergosterol. - While it can cause some GI upset and liver enzyme elevation, it is generally well-tolerated and less associated with acute nephrotoxicity or hypotension compared to Amphotericin B. *Terbinafine* - **Terbinafine** inhibits **squalene epoxidase**, an enzyme involved in ergosterol synthesis, rather than binding directly to ergosterol itself. - Its main side effects include **GI disturbances**, headache, and liver enzyme abnormalities, but typically not the severe nephrotoxicity and hypotension associated with Amphotericin B.

Question 2: A 28-year-old woman with HIV comes to the physician because of an 8-day history of severe pain while swallowing. She has been hospitalized several times with opportunistic infections and has poor adherence to her antiretroviral drug regimen. Endoscopy shows extensive, white, plaque-like lesions in the proximal esophagus. Culture of a biopsy specimen grows Candida albicans. Treatment with intravenous anidulafungin is initiated. Which of the following is the primary mechanism of action of this drug?

A. Binding to tubulin
B. Inhibition of squalene epoxidase
C. Decreased DNA synthesis
D. Binding to ergosterol
E. Decreased glucan synthesis (Correct Answer)

Explanation: ***Decreased glucan synthesis*** - **Anidulafungin** is an **echinocandin** antifungal drug that inhibits the synthesis of **β-(1,3)-D-glucan**, a crucial component of the fungal cell wall. - By disrupting the fungal cell wall, **anidulafungin** causes **osmotic instability** and ultimately leads to cell lysis and death, making it effective against *Candida* infections. *Binding to tubulin* - This is the mechanism of action of **griseofulvin**, an antifungal agent primarily used for dermatophyte infections. - **Griseofulvin** interferes with **microtubule formation**, thus inhibiting fungal mitosis. *Inhibition of squalene epoxidase* - This is the mechanism of action of **terbinafine**, an antifungal drug commonly used for dermatophyte infections like onychomycosis. - **Terbinafine** blocks the synthesis of **ergosterol**, an essential component of the fungal cell membrane, by inhibiting **squalene epoxidase**. *Decreased DNA synthesis* - This mechanism is associated with **flucytosine**, an antifungal agent that is converted to 5-fluorouracil inside fungal cells. - **Flucytosine** then inhibits fungal **DNA and RNA synthesis** and is often used in combination with amphotericin B for severe systemic candidiasis or cryptococcosis. *Binding to ergosterol* - This is the mechanism of action of **polyene antifungals** like **amphotericin B** and **nystatin**. - These drugs bind to **ergosterol** in the fungal cell membrane, forming pores that lead to leakage of intracellular contents and cell death.

Question 3: A 12-year-old girl is brought to the physician for a follow-up examination. Two months ago, she was diagnosed with asthma and treatment was begun with an albuterol inhaler as needed. Since then, she has had episodic chest tightness and cough 2–3 times per week. The cough is intermittent and nonproductive; it is worse at night. She has been otherwise healthy and takes no other medications. Her vital signs are within normal limits. Pulmonary examination shows mild expiratory wheezing of all lung fields. Spirometry shows an FEV1:FVC ratio of 81% and an FEV1 of 80% of predicted; FEV1 rises to 93% of predicted after administration of a short-acting bronchodilator. Treatment with low-dose inhaled beclomethasone is begun. The patient is at greatest risk for which of the following adverse effects?

A. Hypoglycemia
B. Easy bruisability
C. Oropharyngeal candidiasis (Correct Answer)
D. Bradycardia
E. High-pitched voice

Explanation: ***Oropharyngeal candidiasis*** - **Inhaled corticosteroids** like beclomethasone can suppress the local immune response in the oral cavity and pharynx, leading to opportunistic fungal infections. - This condition, commonly known as **thrush**, presents as white patches on the tongue and oral mucosa, which can be mitigated by rinsing the mouth after inhaler use. *Hypoglycemia* - **Inhaled corticosteroids** typically have minimal systemic absorption at low doses and are not associated with hypoglycemia. - **Hypoglycemia** is more commonly associated with diabetes treatment or conditions affecting glucose regulation. *Easy bruisability* - While **systemic corticosteroids** can cause skin thinning and easy bruising with long-term use, **inhaled corticosteroids** at low doses have very limited systemic effects. - The risk of easy bruisability is extremely low with the prescribed treatment in this patient. *Bradycardia* - **Beta-agonists** (like albuterol) can cause tachycardia, but inhaled corticosteroids themselves do not significantly affect heart rate. - **Bradycardia** is not a characteristic adverse effect of beclomethasone; it is typically associated with certain cardiac conditions or medications like beta-blockers. *High-pitched voice* - **Inhaled corticosteroids** can sometimes lead to hoarseness or dysphonia due to local irritation or candidiasis of the vocal cords, but not specifically to a high-pitched voice. - A high-pitched voice is not a recognized adverse effect; rather, a change in voice quality such as hoarseness is more typical.

Question 4: A 45-year-old man presents to the emergency department with difficulties swallowing food. He states that he experiences pain when he attempts to swallow his medications or when he drinks water. He reveals that he was diagnosed with HIV infection five years ago. He asserts that he has been taking his antiretroviral regimen, including emtricitabine, rilpivirine, and tenofovir. His temperature is 98°F (37°C), blood pressure is 100/60 mmHg, pulse is 90/min, respirations are 22/min, and oxygen saturation is 99% on room air. His physical exam is notable for a clear oropharynx, no lymphadenopathy, and a normal cardiac and pulmonary exam. No rashes are noted throughout his body. His laboratory results are displayed below: Hemoglobin: 12 g/dL Hematocrit: 37 % Leukocyte count: 8,000/mm^3 with normal differential Platelet count: 160,000/mm^3 Serum: Na+: 138 mEq/L Cl-: 108 mEq/L K+: 3.5 mEq/L HCO3-: 26 mEq/L BUN: 35 mg/dL Glucose: 108 mg/dL Creatinine: 1.1 mg/dL CD4+ count: 90/mm^3 HIV viral load: 59,000 copies/mL What is the best next step in management?

A. Fluconazole (Correct Answer)
B. Nystatin
C. Oral swab and microscopy
D. Methylprednisolone
E. Esophageal endoscopy and biopsy

Explanation: ***Fluconazole*** - The patient's **odynophagia**, low **CD4+ count**, and high **HIV viral load** are highly suggestive of **esophageal candidiasis**. - **Fluconazole** is the initial empiric treatment of choice for suspected esophageal candidiasis in HIV-positive patients, given its high efficacy and good tolerability. *Nystatin* - **Nystatin** is typically used for **oral candidiasis (thrush)**, which presents with white plaques in the mouth. - The patient has a **clear oropharynx** and **odynophagia**, indicating esophageal involvement, for which nystatin is less effective. *Oral swab and microscopy* - While an **oral swab** can confirm oral candidiasis, it is not sufficient for diagnosing **esophageal candidiasis**. - Given the patient's symptoms of odynophagia and high clinical suspicion in an immunocompromised patient, empiric treatment is preferred over initial diagnostic testing for uncomplicated esophageal candidiasis. *Methylprednisolone* - **Methylprednisolone** is a corticosteroid used to reduce inflammation and is not indicated for the treatment of **candidal infections**. - Using corticosteroids in an immunocompromised patient with an active opportunistic infection could worsen his condition. *Esophageal endoscopy and biopsy* - **Esophageal endoscopy and biopsy** are typically reserved for patients who **fail empiric antifungal therapy** or present with **atypical symptoms** not consistent with candidiasis. - Given the clear clinical picture, initial empiric treatment with fluconazole is the standard first step.

Question 5: A 45-year-old man comes to the physician because of a 3-day history of pain in his mouth and throat and difficulty swallowing. He has a history of COPD, for which he takes theophylline and inhaled budesonide-formoterol. Physical examination shows white patches on the tongue and buccal mucosa that can be scraped off easily. Appropriate pharmacotherapy is initiated. One week later, he returns because of nausea, palpitations, and anxiety. His pulse is 110/min and regular. Physical examination shows a tremor in both hands. Which of the following drugs was most likely prescribed?

A. Amphotericin B
B. Griseofulvin
C. Terbinafine
D. Fluconazole (Correct Answer)
E. Nystatin

Explanation: ***Fluconazole*** - Fluconazole is a potent **CYP450 inhibitor**, specifically **CYP2C9 and CYP3A4**, which can significantly increase the levels of drugs metabolized by these enzymes, such as **theophylline**. - The patient's symptoms of nausea, palpitations, anxiety, tremor, and tachycardia are consistent with **theophylline toxicity**, which would be exacerbated by co-administration with fluconazole. *Amphotericin B* - Amphotericin B is a powerful antifungal, but its primary side effects include **nephrotoxicity**, **infusion-related reactions** (fever, chills, rigors), and **electrolyte disturbances**, not theophylline toxicity. - It is typically reserved for **severe systemic fungal infections** and is not a first-line treatment for uncomplicated **oral candidiasis**. *Griseofulvin* - Griseofulvin is used to treat **dermatophyte infections** (tinea infections) and is not active against *Candida*. - Its main side effects include **gastrointestinal upset**, **headache**, and **photosensitivity**, and it does not significantly interact with theophylline. *Terbinafine* - Terbinafine is an allylamine antifungal primarily used for **dermatophyte infections**, particularly **onychomycosis**, and is not effective for candidiasis. - While it can cause liver enzyme elevation, it does not typically lead to theophylline toxicity or the constellation of symptoms described. *Nystatin* - Nystatin is a **topical or oral non-absorbable antifungal** used for superficial candidal infections, including oral thrush. - It is not absorbed systemically, so it has **virtually no drug interactions** or systemic side effects, and therefore would not cause theophylline toxicity.

Question 6: A 74-year-old man is admitted to the medical ward after he developed a fungal infection. He has aplastic anemia. The most recent absolute neutrophil count was 450/µL. An anti-fungal agent is administered that inhibits the fungal enzyme, (1→3)-β-D-glucan synthase, and thereby disrupts the integrity of the fungal cell wall. He responds well to the treatment. Although amphotericin B is more efficacious for his condition, it was not used because of the side effect profile. What was the most likely infection?

A. Invasive aspergillosis
B. Mucormycosis
C. Histoplasmosis
D. Paracoccidioidomycosis
E. Candidemia (Correct Answer)

Explanation: ***Candidemia*** - The patient's **neutropenia** (absolute neutrophil count of 450/µL) due to aplastic anemia is a major risk factor for invasive candidiasis, including candidemia. - The antifungal agent's mechanism of action, targeting **(1→3)-β-D-glucan synthase**, is characteristic of **echinocandins**, which are first-line agents for candidemia, especially in critically ill or neutropenic patients, and often preferred over amphotericin B due to a better side effect profile. *Invasive aspergillosis* - While neutropenia is a significant risk factor for invasive aspergillosis, the primary antifungal drugs for this condition are typically **voriconazole** or **isavuconazole**, although echinocandins may be used as salvage therapy or in combination. - The description of the drug's mechanism specifically targeting **(1→3)-β-D-glucan synthase** does not make aspergillosis the *most likely* infection, as some Aspergillus species may have less β-D-glucan in their cell walls compared to *Candida*. *Mucormycosis* - This aggressive fungal infection is often seen in immunocompromised patients, particularly those with **diabetes** or profound neutropenia, but the primary treatment is usually **amphotericin B**. - Mucorales fungi typically **lack ergosterol** and their cell walls do not contain **(1→3)-β-D-glucan**, making echinocandins ineffective. *Histoplasmosis* - This is a dimorphic fungal infection endemic to certain geographic regions, primarily affecting the lungs and disseminating in immunocompromised individuals. - The drug of choice for severe or disseminated histoplasmosis is **amphotericin B**, followed by azoles; echinocandins are generally not active against *Histoplasma*. *Paracoccidioidomycosis* - This is a chronic systemic mycosis found in Latin America, primarily affecting the lungs, skin, and lymph nodes. - Treatment for severe forms typically involves **amphotericin B**, followed by sulfonamides or azoles for maintenance; echinocandins are not effective against *Paracoccidioides*.

Question 7: A 57-year-old woman with non-small cell lung cancer comes to the physician 4 weeks after her tumor was resected. She takes no medications. The physician starts her on a treatment regimen that includes vinblastine. This treatment puts the patient at highest risk for which of the following?

A. Pulmonary embolism
B. Invasive fungal infection (Correct Answer)
C. Progressive multifocal leukoencephalopathy
D. Pulmonary fibrosis
E. Heart failure

Explanation: ***Invasive fungal infection*** - Vinblastine is an **antimitotic chemotherapy agent** that, like other chemotherapeutic agents, can cause **myelosuppression**. - **Myelosuppression** (particularly **neutropenia**) severely compromises the immune system, making patients highly susceptible to **opportunistic infections**, including invasive fungal infections. *Pulmonary embolism* - While cancer itself is a risk factor for **venous thromboembolism**, including pulmonary embolism, vinblastine itself **does not directly increase the risk** more than other chemotherapy agents. - The highest risk with vinblastine specifically relates to its impact on bone marrow. *Progressive multifocal leukoencephalopathy* - This is a rare, severe opportunistic infection of the brain caused by the **JC virus**, primarily seen in patients with **severe immunosuppression**, such as those with HIV/AIDS or on chronic immunosuppressive therapy (e.g., natalizumab). - While chemotherapy can cause immunosuppression, PML is not the most common or highest specific risk directly associated with vinblastine or its immediate, acute side effects compared to myelosuppression and opportunistic infections. *Pulmonary fibrosis* - **Pulmonary fibrosis** is a known side effect of certain chemotherapeutic agents like **bleomycin** and **busulfan**, but it is **not a primary or common adverse effect of vinblastine**. - The side effect profile of vinblastine primarily involves myelosuppression, neurotoxicity, and gastrointestinal effects. *Heart failure* - **Cardiotoxicity leading to heart failure** is a significant concern with certain chemotherapy drugs, particularly **anthracyclines** (e.g., doxorubicin) and some tyrosine kinase inhibitors. - **Vinblastine is not typically associated with cardiotoxicity or heart failure** as a primary or high-risk adverse effect.

Question 8: A 46-year-old man with HIV infection comes to the physician because of a 1-week history of severe retrosternal pain while swallowing. He has not been compliant with his antiretroviral drug regimen. His CD4+ T-lymphocyte count is 98/mm3 (N ≥ 500). Endoscopy shows white plaques in the esophagus. The most appropriate immediate treatment is a drug that inhibits which of the following enzymes?

A. DNA polymerase
B. Hydrogen-potassium ATPase
C. Cytochrome p450 enzymes (Correct Answer)
D. Phospholipase A2
E. Squalene epoxidase

Explanation: ***Cytochrome P450 enzymes*** - The patient's symptoms (retrosternal pain on swallowing, white plaques on endoscopy) and severely low **CD4+ count (98/mm³)** are highly suggestive of **esophageal candidiasis**, a common opportunistic infection in AIDS. - **Fluconazole**, an azole antifungal, is the **first-line treatment** for esophageal candidiasis and works by inhibiting **14α-demethylase (lanosterol demethylase)**, a fungal **cytochrome P450 enzyme**. - This inhibition prevents the conversion of lanosterol to ergosterol, disrupting **fungal cell membrane synthesis** and leading to fungal cell death. *Squalene epoxidase* - **Terbinafine** and **naftifine** (allylamine antifungals) inhibit squalene epoxidase in the ergosterol synthesis pathway. - These agents are primarily used for **dermatophyte infections** (onychomycosis, tinea) and have **poor activity against Candida species**. - They are not appropriate for treating esophageal candidiasis. *DNA polymerase* - Inhibitors of **DNA polymerase**, such as acyclovir or ganciclovir, are used to treat **herpesvirus infections** (HSV, CMV). - While herpes esophagitis can occur in immunocompromised patients, it typically presents with **punched-out ulcers**, not white plaques. *Hydrogen-potassium ATPase* - **Proton pump inhibitors** (PPIs) target hydrogen-potassium ATPase in gastric parietal cells to reduce **acid secretion**. - These are used to treat **GERD** or **peptic ulcers**, which do not present with white plaques on endoscopy. - While PPIs may provide symptomatic relief, they do not treat the underlying fungal infection. *Phospholipase A2* - Phospholipase A2 inhibitors are used as **anti-inflammatory agents**, as PLA2 releases arachidonic acid, a precursor to inflammatory mediators. - These drugs have no role in treating fungal infections like esophageal candidiasis.

Question 9: A 69-year-old man with metastatic colon cancer is brought to the emergency department because of shortness of breath, fever, chills, and a productive cough with streaks of blood for the past 5 days. He has a history of emphysema. The patient does not have abdominal pain or headache. He receives chemotherapy with 5-fluorouracil, leucovorin, and oxaliplatin every 6 weeks; his last cycle was 3 weeks ago. His temperature is 38.3°C (101°F), pulse is 112/min, and blood pressure is 100/70 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 83%. A few scattered inspiratory crackles are heard over the right lung. His mucous membranes are dry. Cardiac examination is normal. Laboratory studies show: Hemoglobin 9.3 mg/dL Leukocyte count 700/mm3 Segmented neutrophils 68% Lymphocytes 25% Eosinophils 4% Monocytes 3% Platelet count 104,000/mm3 Serum Glucose 75 mg/dL Urea nitrogen 41 mg/dL Creatinine 2.1 mg/dL Galactomannan antigen Positive Which of the following is the most appropriate initial pharmacotherapy?

A. Ceftriaxone and azithromycin
B. Rifampin, isoniazid, pyrazinamide, and ethambutol
C. Ceftazidime and levofloxacin
D. Piperacillin-tazobactam
E. Voriconazole (Correct Answer)

Explanation: ***Voriconazole*** - The patient has **neutropenic fever** (leukocyte count 700/mm3, recent chemotherapy) with pulmonary symptoms and a positive **galactomannan antigen**, which is highly suggestive of **invasive aspergillosis**. - **Voriconazole** is the recommended first-line agent for the treatment of **invasive aspergillosis**. *Ceftriaxone and azithromycin* - This combination is typically used for **community-acquired pneumonia**, targeting common bacterial pathogens like *Streptococcus pneumoniae* and atypical bacteria. - It does not cover **fungal infections** like aspergillosis, nor does it provide broad-spectrum gram-negative coverage suitable for neutropenic fever. *Rifampin, isoniazid, pyrazinamide, and ethambutol* - This four-drug regimen is the standard treatment for **active tuberculosis**. - There is no clinical or laboratory evidence (e.g., acid-fast bacilli smear, cultures) to suggest tuberculosis in this patient. *Ceftazidime and levofloxacin* - **Ceftazidime** is a third-generation cephalosporin with good gram-negative coverage, including *Pseudomonas*, which might be considered in neutropenic fever. However, it lacks adequate gram-positive coverage. - **Levofloxacin** is a fluoroquinolone that provides broad-spectrum coverage, but this combination still misses the likely fungal pathogen and is not ideal for initial empiric therapy in severe neutropenic fever. *Piperacillin-tazobactam* - **Piperacillin-tazobactam** is a broad-spectrum antibiotic with good coverage against both gram-positive and gram-negative bacteria, including *Pseudomonas aeruginosa*, making it a common choice for **empiric therapy in neutropenic fever**. - However, it does not cover **fungal infections**, which are strongly indicated by the positive **galactomannan antigen** in this immunocompromised patient.

Question 10: A 45-year-old HIV-positive male presents to his primary care physician complaining of decreased libido. He reports that he has been unable to maintain an erection for the past two weeks. He has never encountered this problem before. He was hospitalized four weeks ago for cryptococcal meningitis and has been on long-term antifungal therapy since then. His CD4 count is 400 cells/mm^3 and viral load is 5,000 copies/ml. He was previously non-compliant with HAART but since his recent infection, he has been more consistent with its use. His past medical history is also notable for hypertension, major depressive disorder, and alcohol abuse. He takes lisinopril and sertraline. His temperature is 98.6°F (37°C), blood pressure is 120/85 mmHg, pulse is 80/min, and respirations are 18/min. The physician advises the patient that side effects like decreased libido may manifest due to a drug with which of the following mechanisms of action?

A. Inhibition of beta-glucan synthesis
B. Formation of pores in cell membrane
C. Inhibition of ergosterol synthesis (Correct Answer)
D. Disruption of microtubule formation
E. Inhibition of pyrimidine synthesis

Explanation: ***Inhibition of ergosterol synthesis*** - The patient was recently treated for **cryptococcal meningitis** and is likely on an **azole antifungal**, such as fluconazole or itraconazole, for long-term therapy. - Azole antifungals inhibit **14-alpha-demethylase**, an enzyme crucial for **ergosterol synthesis**, and are known to cause endocrine side effects like **decreased libido** and **erectile dysfunction** due to their impact on steroid hormone synthesis. *Inhibition of beta-glucan synthesis* - This mechanism of action belongs to **echinocandins** (e.g., caspofungin, micafungin), which inhibit the synthesis of **1,3-beta-D-glucan**, a key component of the fungal cell wall. - Echinocandins are typically used for *Candida* infections and are generally not associated with significant endocrine side effects like decreased libido or erectile dysfunction. *Formation of pores in cell membrane* - This is the mechanism of action for **polyene antifungals** like **amphotericin B** and **nystatin**, which bind to ergosterol in the fungal cell membrane, creating pores and leading to cell lysis. - While effective against *Cryptococcus*, amphotericin B is primarily used for acute, severe infections due to its significant toxicity, including nephrotoxicity, and is not typically used for long-term maintenance in this context with libido as the main symptom. *Disruption of microtubule formation* - This mechanism is characteristic of **griseofulvin**, an antifungal primarily used for dermatophyte infections of the skin and nails. - It interferes with **microtubule function** and inhibits fungal mitosis, but it is not used for systemic fungal infections like cryptococcal meningitis, nor is it commonly associated with decreased libido. *Inhibition of pyrimidine synthesis* - This mechanism belongs to **flucytosine**, which is converted to **5-fluorouracil** within fungal cells, inhibiting DNA and RNA synthesis. - Flucytosine is typically used in combination with amphotericin B for severe cryptococcal infections, but it is not known to cause decreased libido as a common or prominent side effect.

Question 11: An 11-year-old boy with HIV and esophageal candidiasis is being treated with caspofungin. What is the mechanism of action of this drug?

A. Pore formation in cell membranes
B. Inhibition of ergosterol synthesis
C. Inhibition of 1,3-Beta-glucan synthase (Correct Answer)
D. Inhibition of squalene epoxidase
E. Inhibition of pyrimidine synthesis

Explanation: ***Inhibition of 1,3-Beta-glucan synthase*** - **Caspofungin** is an **echinocandin** antifungal agent that works by inhibiting **1,3-beta-D-glucan synthase**. - This enzyme is crucial for the synthesis of **glucan**, a vital component of the **fungal cell wall**, leading to cell wall disruption and fungal cell death. *Pore formation in cell membranes* - This mechanism of action is characteristic of **polyene antifungals** like **amphotericin B**. - These drugs bind to **ergosterol** in the fungal cell membrane, forming pores that lead to leakage of cellular contents. *Inhibition of ergosterol synthesis* - This is the mechanism of action for **azole antifungals** (e.g., fluconazole, itraconazole) and **allylamines** (e.g., terbinafine). - Azoles inhibit **14-alpha-demethylase**, an enzyme involved in converting lanosterol to ergosterol, while allylamines inhibit **squalene epoxidase**. *Inhibition of squalene epoxidase* - This is the specific mechanism for **allylamine antifungals** like **terbinafine**. - Inhibition of **squalene epoxidase** prevents the synthesis of **ergosterol**, primarily used for superficial fungal infections. *Inhibition of pyrimidine synthesis* - This mechanism is characteristic of **flucytosine**, an antifungal pro-drug. - Flucytosine is converted to **5-fluorouracil** within fungal cells, which then inhibits fungal DNA and RNA synthesis.

Question 12: A 38-year-old man comes to the physician because of white lesions in his mouth for 4 days. He also has intense pain while chewing food. He was diagnosed with non-Hodgkin lymphoma around 8 months ago. He is undergoing chemotherapy and is currently on his fourth cycle. He was treated for herpes labialis 4 months ago with acyclovir. He has smoked half a pack of cigarettes daily for 15 years. He appears healthy. Vital signs are within normal limits. Cervical and axillary lymphadenopathy is present. Oral examination shows white plaques on his tongue and buccal mucosa that bleed when scraped off. The remainder of the examination shows no abnormalities. Which of the following is the next best step in management?

A. Biopsy of a lesion
B. Culture of the lesions
C. Topical corticosteroids
D. Intravenous fluconazole
E. Topical nystatin (Correct Answer)

Explanation: ***Topical nystatin*** - The patient's presentation with **oral white plaques that bleed when scraped**, combined with recent **chemotherapy** and immunodeficiency due to non-Hodgkin lymphoma, is highly suggestive of **oral candidiasis (thrush)**. - **Topical antifungal agents** like nystatin are the first-line treatment for uncomplicated oral candidiasis, especially in immunocompromised patients, effectively targeting the fungal overgrowth. *Biopsy of a lesion* - While a biopsy might be considered for atypical or persistent lesions, the classic presentation of **scrappable white plaques** in an immunocompromised patient makes **oral candidiasis** highly likely, and empiric antifungal treatment is usually initiated first. - Doing a biopsy would delay treatment and is not the most immediate or appropriate next step given the clear clinical picture. *Culture of the lesions* - A culture could confirm the presence of Candida species and help determine antifungal susceptibility, but it is **not typically the immediate next step** in managing suspected oral candidiasis. - The clinical picture is strong enough to warrant empiric treatment, and a culture can be considered later if the patient does not respond to initial therapy. *Topical corticosteroids* - **Corticosteroids** are used to reduce inflammation and are contraindicated here as the lesions are infective in origin. - Using corticosteroids in a patient with an active fungal infection would worsen the condition by further **suppressing the immune response** and promoting fungal growth. *Intravenous fluconazole* - **Intravenous fluconazole** would be appropriate for **severe or disseminated candidiasis**, or if the patient fails to respond to topical or oral antifungal agents. - Given that the patient's symptoms are localized to the mouth and he appears relatively healthy otherwise (vital signs normal), a less aggressive, topical approach is appropriate initially.

Question 13: A 42-year-old man comes to the physician because he is concerned that he is balding. Over the past few months, he has noticed patchy areas of hair loss on his head. He also mentions that he has felt depressed since the death of his wife last year and has unintentionally lost about 18 kg (40 lbs). He is constantly fatigued. He has little appetite because he feels food does not taste the same way anymore. He also has occasional episodes of watery diarrhea. He drinks 5–6 cans of beer daily. Vital signs are within normal limits. Examination shows dry, scaly skin on both feet. There is patchy alopecia of the scalp, axillae, chest, and mons pubis. Which of the following is most likely to directly improve this patient's alopecia?

A. Finasteride
B. Behavioral therapy
C. Restriction of vitamin A-rich foods
D. Zinc supplementation (Correct Answer)
E. Griseofulvin

Explanation: ***Zinc supplementation*** - The patient's symptoms, including **patchy alopecia**, **dry scaly skin**, **weight loss**, **fatigue**, **depressed mood**, **taste alteration**, and **diarrhea**, are highly suggestive of **zinc deficiency**. - Alcoholism also contributes to zinc malabsorption, thus **zinc supplementation** directly addresses the underlying cause of the alopecia. *Finasteride* - **Finasteride** is used for **androgenetic alopecia** (male-pattern baldness), which typically presents as diffuse thinning or receding hairline, not patchy hair loss in various body areas. - It works by inhibiting 5-alpha reductase, reducing the conversion of **testosterone to dihydrotestosterone**, which is not the pathogenesis of this patient's alopecia. *Behavioral therapy* - While the patient's **depression** and **alcohol use** could benefit from behavioral therapy, it would not directly address the **alopecia** or other physical manifestations of **zinc deficiency**. - Behavioral therapy focuses on psychological and lifestyle factors, not specific nutritional deficiencies causing hair loss. *Restriction of vitamin A-rich foods* - **Hypervitaminosis A** can cause alopecia, but the patient's symptoms (diarrhea, altered taste, scaly skin) are not consistent with **vitamin A toxicity**. - Restricting these foods would be inappropriate and potentially harmful given the patient's likely **malnutrition**. *Griseofulvin* - **Griseofulvin** is an antifungal medication used to treat **tinea capitis** (ringworm of the scalp), which presents as patchy hair loss often with inflammation, itching, and scaling. - While it causes patchy hair loss, the patient's other systemic symptoms (taste changes, diarrhea, generalized skin involvement, and potential alcoholism) point away from a purely fungal infection and towards a **nutritional deficiency**.

Question 14: A 41-year-old man comes to the physician because of a 3-week history of fatigue, cough, and a 4.5-kg (10-lb) weight loss. He does not smoke or drink alcohol. He appears emaciated. A chest x-ray shows a calcified nodule in the left lower lobe and left hilar lymphadenopathy. The physician initiates therapy for the condition and informs him that he will have to return for monthly ophthalmologic examination for the next 2 months. These examinations are most likely to evaluate the patient for an adverse effect of a drug with which of the following mechanisms of action?

A. Impaired synthesis of mycolic acids
B. Impaired protein synthesis due to binding to 50S ribosomes
C. Impaired production of hemozoin from heme
D. Impaired synthesis of cell wall polysaccharides (Correct Answer)
E. Impaired protein synthesis due to binding to 30S ribosomes

Explanation: ***Impaired synthesis of cell wall polysaccharides*** - The patient's clinical presentation (fatigue, cough, weight loss, calcified nodule, hilar lymphadenopathy) is classic for **tuberculosis**. - The requirement for **monthly ophthalmologic examinations** is pathognomonic for **ethambutol** therapy, as this drug causes **optic neuritis** (decreased visual acuity, red-green color blindness). - **Ethambutol** inhibits **arabinosyl transferase**, which impairs the synthesis of **arabinogalactan**, a key polysaccharide component of the mycobacterial cell wall. - Due to the risk of optic neuritis, patients on ethambutol require baseline and monthly ophthalmologic monitoring, especially during the first 2 months of therapy. *Impaired synthesis of mycolic acids* - This describes the mechanism of **isoniazid (INH)**, a first-line anti-TB drug that inhibits mycolic acid synthesis. - The main adverse effects of isoniazid are **peripheral neuropathy** (prevented with pyridoxine/vitamin B6) and **hepatotoxicity**, not optic neuritis. - Isoniazid does not require routine ophthalmologic monitoring. *Impaired protein synthesis due to binding to 50S ribosomes* - This mechanism describes **macrolides** (e.g., clarithromycin, azithromycin) and **chloramphenicol**. - While macrolides may be used for atypical mycobacterial infections, they are not first-line TB therapy and do not cause optic neuritis requiring monthly eye exams. *Impaired protein synthesis due to binding to 30S ribosomes* - This mechanism describes **aminoglycosides** (e.g., streptomycin) and **tetracyclines**. - While streptomycin is a second-line anti-TB drug, its main adverse effects are **ototoxicity** (hearing loss, vestibular dysfunction) and **nephrotoxicity**, not optic neuritis. - These drugs do not require ophthalmologic monitoring. *Impaired production of hemozoin from heme* - This is the mechanism of **chloroquine** and **hydroxychloroquine**, which are antimalarial drugs. - While chloroquine can cause retinopathy requiring ophthalmologic monitoring, this patient has **tuberculosis**, not malaria. - The clinical scenario (calcified lung nodule, hilar lymphadenopathy) and TB treatment context make this mechanism incorrect for this case.

Question 15: A 72-year-old woman with type 2 diabetes mellitus comes to the physician because she is concerned about the appearance of her toenails. Examination shows yellowish discoloration of all toenails on both feet. The edges of the toenails are lifted, and there is subungual debris. Potassium hydroxide preparation of scrapings from the nails shows multiple branching septate hyphae. Treatment with oral terbinafine is begun. Which of the following is the primary mechanism of action of this drug?

A. Inhibition of squalene epoxidase (Correct Answer)
B. Formation of pores in cell membrane
C. Inhibition of β-glucan synthesis
D. Interference with mitosis during metaphase
E. Prevention of lanosterol to ergosterol conversion

Explanation: ***Inhibition of squalene epoxidase*** - **Terbinafine** is an **allylamine** antifungal that inhibits the enzyme **squalene epoxidase**, an early step in fungal ergosterol synthesis - This inhibition leads to the accumulation of **squalene**, which is toxic to the fungal cell, and a deficiency of **ergosterol**, disrupting cell membrane integrity and function - Terbinafine is highly effective for **onychomycosis** (fungal nail infections) caused by dermatophytes *Formation of pores in cell membrane* - This mechanism is characteristic of **polyene antifungals** like **amphotericin B** and **nystatin** - These drugs bind to **ergosterol** in the fungal cell membrane, creating pores that lead to leakage of intracellular contents and cell death *Inhibition of β-glucan synthesis* - This is the primary mechanism of action for **echinocandin** antifungals, such as **caspofungin**, **micafungin**, and **anidulafungin** - These drugs inhibit **(1,3)-β-D-glucan synthase**, which is essential for the synthesis of glucan, a major component of the fungal cell wall *Interference with mitosis during metaphase* - This mechanism is characteristic of **griseofulvin**, another antifungal agent used for dermatophyte infections - **Griseofulvin** interferes with **microtubule function**, disrupting mitotic spindle formation and preventing fungal cell division *Prevention of lanosterol to ergosterol conversion* - This mechanism is associated with **azole antifungals** (e.g., fluconazole, itraconazole), which inhibit fungal **cytochrome P450-dependent 14-α-demethylase** - This enzyme is responsible for the conversion of **lanosterol** to **ergosterol**, leading to ergosterol depletion and accumulation of toxic sterol precursors

Question 16: You are taking care of a patient with renal failure secondary to anti-fungal therapy. The patient is a 66-year-old male being treated for cryptococcal meningitis. This drug has a variety of known side effects including acute febrile reactions to infusions, anemia, hypokalemia and hypomagnesemia. What is the mechanism of action of this drug?

A. Inhibition of squalene epoxidase
B. Binding of the 50S subunit
C. Pore formation secondary to ergosterol binding (Correct Answer)
D. Disruption of microtubule formation
E. Inhibition of 1,3-beta-glucan synthase

Explanation: ***Pore formation secondary to ergosterol binding*** - This describes the mechanism of action of **amphotericin B**, the antifungal agent used for cryptococcal meningitis. - Amphotericin B binds to **ergosterol** in the fungal cell membrane, leading to the formation of pores, disruption of membrane integrity, and ultimately cell death. - The side effects described—**nephrotoxicity with renal failure, hypokalemia, and hypomagnesemia**—are classic adverse effects of amphotericin B due to its effect on renal tubular cells and electrolyte wasting. *Inhibition of squalene epoxidase* - This is the mechanism of action for **terbinafine**, an antifungal primarily used for dermatophyte infections (e.g., onychomycosis), not systemic infections like cryptococcal meningitis. - Terbinafine inhibits ergosterol synthesis at an earlier step but does not cause the severe nephrotoxicity and electrolyte disturbances described. *Binding of the 50S subunit* - This mechanism of action is characteristic of **macrolide antibiotics** like azithromycin or clarithromycin, which are antibacterial agents, not antifungals. - These drugs inhibit bacterial protein synthesis and are ineffective against fungal infections. *Disruption of microtubule formation* - This is the mechanism of action for **griseofulvin**, an antifungal drug used for dermatophyte infections of the skin, hair, and nails. - Griseofulvin interferes with fungal cell division and is not used for life-threatening systemic infections like cryptococcal meningitis. *Inhibition of 1,3-beta-glucan synthase* - This mechanism is associated with **echinocandins** (e.g., caspofungin, micafungin), which inhibit fungal cell wall synthesis. - While echinocandins are used for some systemic fungal infections (particularly Candida and Aspergillus), they do not typically cause the severe renal failure and electrolyte disturbances characteristic of amphotericin B.

Question 17: A 26-year-old man comes to the physician because of discoloration of the toenails. He has a history of peptic ulcer disease treated with pantoprazole. The physician prescribes oral itraconazole for a fungal infection and temporarily discontinues pantoprazole. Which of the following best describes the reason for discontinuing pantoprazole therapy?

A. Decreased therapeutic effect of itraconazole due to cytochrome P450 induction
B. Increased toxicity of itraconazole due to cytochrome P450 induction
C. Decreased therapeutic effect of itraconazole due to decreased absorption (Correct Answer)
D. Increased toxicity of itraconazole due to decreased protein binding
E. Decreased therapeutic effect of itraconazole due to cytochrome P450 inhibition

Explanation: ***Decreased therapeutic effect of itraconazole due to decreased absorption*** - **Itraconazole** requires an **acidic gastric pH** for optimal absorption, as it is a weakly basic drug. - **Pantoprazole**, a proton pump inhibitor, significantly raises gastric pH, thereby reducing itraconazole's absorption and its therapeutic effect. *Decreased therapeutic effect of itraconazole due to cytochrome p450 induction* - **Pantoprazole** does not primarily induce significant **cytochrome P450 enzymes** in a way that would lead to a clinically relevant decrease in itraconazole's therapeutic effect. - While some PPIs can interact with CYP enzymes, this is not the main reason for discontinuing pantoprazole with itraconazole. *Increased toxicity of itraconazole due to cytochrome p450 induction* - **Cytochrome P450 induction** would generally lead to faster metabolism and **decreased levels of itraconazole**, thus reducing its efficacy rather than increasing its toxicity. - This interaction mechanism is contrary to the clinical concern of increased toxicity. *Decreased therapeutic effect of itraconazole due to cytochrome p450 inhibition* - While both **pantoprazole** and **itraconazole** can interact with **cytochrome P450 enzymes** (itraconazole is a strong CYP3A4 inhibitor, and pantoprazole can be a weak CYP2C19 inhibitor), the primary concern when co-administering them is not a decrease in itraconazole's effect due to pantoprazole's P450 inhibition. - If anything, inhibition of itraconazole's metabolism would theoretically increase its levels, which is not the reason for drug discontinuation. *Increased toxicity of itraconazole due to decreased protein binding* - There is no significant evidence that **pantoprazole** widely affects the **protein binding** of **itraconazole** to an extent that would lead to increased toxicity. - Alterations in protein binding are not the primary mechanism behind this specific drug interaction.

Question 18: A 73-year-old man presents to the office, complaining of “weird blisters” on his right hand, which appeared 2 weeks ago. The patient says that he initially had a rash, which progressed to blisters. He denies any trauma or known contact with sick people. He is worried because he hasn’t been able to garden since the rash appeared, and he was planning on entering his roses into an annual competition this month. His vital signs are stable. On physical exam, the patient has multiple bullae accompanied by red, papular lesions on his right hand, which progress to his forearm. The right axillary lymph nodes are swollen and tender. What is the treatment for the most likely diagnosis of this patient?

A. Itraconazole (Correct Answer)
B. Azithromycin
C. Topical corticosteroids
D. Doxycycline
E. Potassium iodide solution

Explanation: ***Itraconazole*** - This patient likely has **sporotrichosis**, a subcutaneous fungal infection, given the history of **gardening** (exposure to soil/plants), **papular lesions progressing to blisters**, and **lymphatic spread** (swollen axillary lymph nodes). - **Itraconazole** is the **first-line treatment** for cutaneous and lymphocutaneous sporotrichosis. *Azithromycin* - **Azithromycin** is an **antibiotic** used to treat bacterial infections, not fungal infections like sporotrichosis. - It is often used for respiratory tract infections, sexually transmitted infections, and some skin infections. *Topical corticosteroids* - **Topical corticosteroids** are anti-inflammatory agents that would likely worsen a fungal infection by suppressing the immune response. - They are used for inflammatory dermatoses like eczema or psoriasis and would not be effective against sporotrichosis. *Doxycycline* - **Doxycycline** is a broad-spectrum **antibiotic**, effective against a variety of bacterial infections, including some atypical pathogens. - It has no antifungal activity and would not be an appropriate treatment for sporotrichosis. *Potassium iodide solution* - While traditionally used for sporotrichosis, **potassium iodide (KI) solution** is now considered a **second-line treatment** due to its side effects and the availability of more effective and safer antifungals like itraconazole. - It is used only in cases where itraconazole is contraindicated or ineffective.

Question 19: A potassium hydroxide preparation is conducted on a skin scraping of the hypopigmented area. Microscopy of the preparation shows long hyphae among clusters of yeast cells. Based on these findings, which of the following is the most appropriate pharmacotherapy?

A. Topical corticosteroid
B. Oral ketoconazole
C. Topical selenium sulfide (Correct Answer)
D. Topical nystatin
E. Oral fluconazole

Explanation: ***Topical selenium sulfide*** - The presence of **long hyphae** and **clusters of yeast cells** on KOH prep is characteristic of **tinea versicolor**, caused by *Malassezia furfur*. - **Selenium sulfide** is a common and effective topical antifungal agent for tinea versicolor, available in shampoos and lotions. *Topical corticosteroid* - **Corticosteroids** have anti-inflammatory properties but do not treat fungal infections. - Using corticosteroids alone would only mask symptoms and could potentially worsen the fungal infection. *Oral ketoconazole* - While **oral ketoconazole** is an antifungal, it is generally reserved for extensive or recalcitrant cases of tinea versicolor due to potential systemic side effects, such as **hepatotoxicity**. - **Topical treatments** are preferred as first-line therapy for localized infections like this one. *Topical nystatin* - **Nystatin** is an antifungal agent primarily effective against *Candida* species. - It is **not effective** against *Malassezia furfur*, the causative agent of tinea versicolor. *Oral fluconazole* - **Oral fluconazole** is an effective systemic antifungal used for various *Candida* and dermatophyte infections. - Similar to oral ketoconazole, it is typically reserved for **widespread or recalcitrant cases** of tinea versicolor, with topical therapy being the preferred initial approach.

Question 20: A 51-year-old man with a history of severe persistent asthma is seen today with the complaint of white patches on his tongue and inside his mouth. He says this all started a couple of weeks ago when he recently started a new medication for his asthma. The vital signs include: temperature 36.7°C (98.0°F), blood pressure 126/74 mm Hg, heart rate 74/min, and respiratory rate 14/min. His physical examination is significant for mild bilateral wheezes, and attempts at scraping off the lesions in the mouth are successful but leave erythema underlying where they were removed. Which of the following medications is responsible for his presentation?

A. Theophylline
B. Omalizumab
C. Beclomethasone inhaler (Correct Answer)
D. Salmeterol inhaler
E. Over-use of the albuterol inhaler

Explanation: ***Beclomethasone inhaler*** - The patient's oral **white patches** are consistent with **oral candidiasis (thrush)**, a common side effect of **inhaled corticosteroids** such as **beclomethasone**. - This occurs because inhaled corticosteroids can suppress the local immune response in the oral cavity, allowing *Candida albicans* to overgrow, especially if the mouth is not rinsed after use. *Theophylline* - Theophylline is a **bronchodilator** and its common side effects are primarily systemic, including **nausea, vomiting, headache, and tremors**, especially at toxic levels. - It does not typically cause oral candidiasis or white patches in the mouth. *Omalizumab* - Omalizumab is a **monoclonal antibody** used for **severe asthma** that targets IgE. Side effects are often related to **injection site reactions**, and in rare cases, hypersensitivity reactions. - It is not associated with the development of oral candidiasis. *Salmeterol inhaler* - Salmeterol is a **long-acting beta-2 agonist (LABA)** used as a bronchodilator. Common side effects include **tremor, palpitations, and headache**. - It does not contain steroids and therefore does not cause oral candidiasis. *Over-use of the albuterol inhaler* - Albuterol is a **short-acting beta-2 agonist (SABA)** used as a rescue inhaler. Overuse can lead to systemic effects like **tremor, tachycardia, and palpitations**. - Like salmeterol, it is not a steroid and does not cause oral candidiasis; the white patches described are not a side effect of albuterol.

Question 21: A 24-year-old professional wrestler recently participated in a charitable tournament event in Bora Bora, a tropical island that is part of the French Polynesia Leeward Islands. During his stay, he wore tight-fitting clothes and tight bathing trunks for extended periods. After 6 days, he observed symmetric, erythematous itchy rash in his groin, with a significant amount of moisture and scales. Central areas of the rash were hyperpigmented, and the border was slightly elevated and sharply demarcated. His penis and scrotum were not affected. He immediately visited a local dermatology clinic where a specialist conducted a Wood lamp examination to exclude the presence of a bacterial infection (primary infection due to Corynebacterium minutissimum). The working diagnosis was a fungal infection. Which topical agent should be recommended to treat this patient?

A. Nystatin
B. Ketoconazole
C. Miconazole
D. Betamethasone/clotrimazole combination
E. Terbinafine (Correct Answer)

Explanation: ***Terbinafine*** - This patient presents with symptoms highly suggestive of **tinea cruris** (jock itch), a fungal infection of the groin, which is effectively treated with topical **allylamines** like terbinafine. - **Terbinafine** acts by inhibiting **squalene epoxidase**, an enzyme essential for fungal ergosterol synthesis, leading to fungicidal activity against dermatophytes. *Nystatin* - **Nystatin** is a fungicide primarily effective against **Candida species**, which typically cause diaper rash or intertrigo in skin folds, characterized by satellite lesions. - The presented description with elevated borders and scales, but unaffected penis/scrotum, is less typical for **Candidiasis**. *Ketoconazole* - **Ketoconazole** is an **azole antifungal** that inhibits 14-α-demethylase, an enzyme necessary for ergosterol synthesis. It is effective against dermatophytes but can be associated with skin irritation when used topically. - While effective, **allylamines** like terbinafine are often preferred for dermatophyte infections due to their fungicidal action. *Miconazole* - Similar to ketoconazole, **miconazole** is an **imidazole antifungal** (an azole derivative) that inhibits ergosterol synthesis. - While effective against dermatophytes like those causing tinea cruris, **terbinafine** is often considered more potent and achieves faster clearance for dermatophyte infections. *Betamethasone/clotrimazole combination* - While **clotrimazole** is an antifungal, the addition of **betamethasone** (a potent corticosteroid) is generally **contraindicated** for primary fungal infections. - Corticosteroids can **mask the infection**, potentially worsen it by suppressing the local immune response, and lead to steroid-induced skin changes, such as atrophy.

Question 22: A 23-year-old female presents to the emergency department complaining of a worsening headache. The patient reports that the headache started one month ago. It is constant and “all over” but gets worse when she is lying down or in the setting of bright lights. Review of systems is significant for low-grade fever, night sweats, cough, malaise, poor appetite, and unintentional weight loss of 12 pounds in the last two months. The patient is sexually active with multiple male partners and reports inconsistent condom use. She has a history of intravenous drug use, and has not been to a doctor in the last two years. The patient’s temperature is 100.4°F (38.0°C), blood pressure is 110/78 mmHg, pulse is 88/min, and respirations are 14/min with an oxygen saturation of 98% O2 on room air. On physical exam, pain is elicited upon passive flexion of the patient’s neck. A CT scan shows ventricular enlargement. A CD4+ count is 57 cells/µL blood. A lumbar puncture is performed with the following findings: Cerebrospinal fluid: Opening pressure: 210 mmH2O Glucose: 32 mg/dL Protein: 204 mg/dL India ink stain: Positive Leukocyte count and differential: Leukocyte count: 200/mm^3 Lymphocytes: 100% Red blood cell count: 2 What is the next best step in therapy?

A. Administer fluconazole
B. Administer dexamethasone
C. Administer vancomycin and ceftriaxone
D. Administer acyclovir
E. Administer amphotericin B and 5-flucytosine (Correct Answer)

Explanation: ***Administer amphotericin B and 5-flucytosine*** - The patient's presentation with **prolonged headache**, **night sweats**, **weight loss**, **fevers**, and **meningeal signs** in the setting of **HIV risk factors** (IV drug use, multiple sexual partners) and a **CD4 count of 57 cells/µL** is highly suggestive of an **opportunistic infection**. - The CSF findings of **elevated opening pressure**, **low glucose**, **high protein**, predominantly **lymphocytic pleocytosis**, and a **positive India ink stain** are classic for **Cryptococcal meningitis**. The **initial treatment** for cryptococcal meningitis in immunocompromised patients is induction therapy with **Amphotericin B** and **5-flucytosine**. *Administer fluconazole* - **Fluconazole** is used for **consolidation** and **maintenance therapy** following initial induction therapy for cryptococcal meningitis, but it is **not sufficient for initial treatment** of severe infections like meningitis, especially in immunocompromised patients. - Monotherapy with fluconazole would have a **higher risk of treatment failure** and relapse in this acute, severe presentation. *Administer dexamethasone* - **Dexamethasone** (a corticosteroid) is generally **not recommended** for the routine treatment of cryptococcal meningitis and may even be **detrimental** due to its immunosuppressive effects in an already immunocompromised patient. - While steroids are sometimes used in other forms of meningitis (e.g., bacterial meningitis to reduce inflammation), their role in fungal meningitis is limited and can worsen outcomes. *Administer vancomycin and ceftriaxone* - **Vancomycin** and **ceftriaxone** are **antibiotics** used to treat **bacterial meningitis**. - The patient's CSF findings (lymphocytic predominance, positive India ink stain) clearly indicate a **fungal infection** (**Cryptococcus**), not bacterial, rendering these antibiotics ineffective. *Administer acyclovir* - **Acyclovir** is an **antiviral agent** used to treat **herpes simplex virus (HSV)** and **varicella-zoster virus (VZV)** infections. - There is **no evidence** in the CSF findings (e.g., specific viral PCR results) or clinical presentation to suggest a viral encephalitis or meningitis requiring acyclovir.

Question 23: A 43-year-old man is brought to the physician for a follow-up examination. He has a history of epilepsy that has been treated with a stable dose of phenytoin for 15 years. He was recently seen by another physician who added a drug to his medications, but he cannot recall the name. Shortly after, he started noticing occasional double vision. Physical examination shows slight vertical nystagmus and gait ataxia. Which of the following drugs was most likely added to this patient's medication regimen?

A. Omeprazole
B. Sertraline
C. St. John's Wort
D. Amiodarone (Correct Answer)
E. Fluconazole

Explanation: ***Amiodarone*** - **Amiodarone** is an individual among drugs that **inhibit cytochrome P450 enzymes**. **Phenytoin** is metabolized by CYP450, and its levels can increase significantly when a CYP450 inhibitor is co-administered, leading to phenytoin toxicity. - The patient's symptoms of **double vision**, **vertical nystagmus**, and **gait ataxia** are classic signs of **phenytoin toxicity**. *Fluconazole* - **Fluconazole** is a potent inhibitor of **CYP450 enzymes**, particularly **CYP2C9** and **CYP2C19**. - While it can increase phenytoin levels and lead to toxicity, **amiodarone** is also a strong inhibitor and is a plausible option in this context. *Omeprazole* - **Omeprazole** is also a **CYP2C19 inhibitor**, meaning it can reduce the metabolism of phenytoin. - However, the effect of **omeprazole** on phenytoin levels is typically less pronounced compared to amiodarone or fluconazole, and the clinical picture points more strongly to a significant drug interaction. *Sertraline* - **Sertraline** is a **selective serotonin reuptake inhibitor (SSRI)** that can inhibit several **CYP450 enzymes**, including **CYP2D6** and to a lesser extent **CYP2C19** and **CYP3A4**. - While it has the potential to interact with phenytoin, its inhibitory effect is generally weaker than other options and less likely to cause such severe toxicity symptoms in this scenario. *St. John's Wort* - **St. John's Wort** is known to be a **CYP450 inducer**, primarily **CYP3A4**. - As an inducer, it would **decrease phenytoin levels**, potentially worsening seizure control but not causing toxicity symptoms like nystagmus and ataxia.

Question 24: A 60-year-old woman comes to the physician because of a 2-week history of severe, retrosternal chest pain. She also has pain when swallowing solid food and medications. She has hypertension, type 2 diabetes mellitus, poorly-controlled asthma, and osteoporosis. She was recently admitted to the hospital for an acute asthma exacerbation that was treated with bronchodilators and a 7-day course of oral corticosteroids. Her current medications include aspirin, amlodipine, metformin, insulin, beclomethasone and albuterol inhalers, and alendronate. Vital signs are within normal limits. Examination of the oral pharynx appears normal. The lungs are clear to auscultation. An upper endoscopy shows a single punched-out ulcer with normal surrounding mucosa at the gastroesophageal junction. Biopsies of the ulcer are taken. Which of the following is the most appropriate next step in management?

A. Start pantoprazole
B. Start fluconazole
C. Discontinue alendronate (Correct Answer)
D. Start ganciclovir
E. Discontinue amlodipine

Explanation: **_Discontinue alendronate (Correct)_** - The patient's presentation with **severe retrosternal chest pain**, **odynophagia**, and a **punched-out ulcer** at the gastroesophageal junction is highly suggestive of **pill esophagitis**. - **Alendronate**, a bisphosphonate, is a common cause of pill esophagitis due to its corrosive properties when prolonged contact with the esophageal mucosa occurs. - The most appropriate next step is to **discontinue the offending medication** to prevent further esophageal injury and allow healing. *Start pantoprazole (Incorrect)* - While proton pump inhibitors (PPIs) like pantoprazole are used for **acid-related esophageal disorders** and can help with symptom relief and healing, the primary cause here is likely medication-induced. - Adding a PPI without addressing the offending agent (alendronate) would be ineffective and not the most appropriate first step, though it may be used adjunctively. *Start fluconazole (Incorrect)* - **Fluconazole** is an antifungal medication indicated for **fungal esophagitis**, most commonly caused by Candida species. - Candidal esophagitis typically presents with **multiple shallow ulcers** or white plaques, not a single punched-out ulcer, and is more common in immunocompromised individuals. - This patient lacks risk factors for candidal infection and has a characteristic appearance of pill esophagitis. *Start ganciclovir (Incorrect)* - **Ganciclovir** is an antiviral medication used to treat **cytomegalovirus (CMV) esophagitis**. - CMV esophagitis usually presents as **large, shallow ulcers** and is primarily seen in immunocompromised patients (HIV/AIDS, transplant recipients), which this patient is not. - A brief course of oral corticosteroids does not cause sufficient immunosuppression to predispose to CMV esophagitis. *Discontinue amlodipine (Incorrect)* - **Amlodipine**, a calcium channel blocker, can cause **gastroesophageal reflux** by relaxing the lower esophageal sphincter, potentially contributing to reflux esophagitis. - However, classic pill esophagitis with a discrete punched-out ulcer is almost exclusively associated with direct mucosal injury from medications like bisphosphonates, tetracyclines, or NSAIDs, rather than reflux-mediated injury alone.

Question 25: A 21-year-old African American female presents to her primary care physician reporting a history of excess hair growth. She has to shave her face and chest on a regular basis. She is sexually active and uses condoms for protection. Her last period was two months ago and she reports having 5-6 menstrual periods per year at irregular intervals. She has no past medical history and takes no medications. She drinks socially and does not smoke. Her family history is notable for heart disease in her father and endometrial cancer in her mother. Her temperature is 98.6°F (37°C), blood pressure is 125/85 mmHg, pulse is 95/min, and respirations are 16/min. The physician considers starting the patient on a medication that is also indicated in the treatment of histoplasmosis. This medication primary acts by inhibiting which of the following proteins?

A. 1,3-beta-glucan synthase
B. 5-alpha-reductase
C. Squalene epoxidase
D. Aromatase
E. Desmolase (Correct Answer)

Explanation: ***Desmolase*** - The clinical presentation of **hirsutism** and **oligomenorrhea** in an African American female is highly suggestive of **polycystic ovary syndrome (PCOS)**. - **Ketoconazole**, an antifungal medication used for histoplasmosis, also non-selectively inhibits **cytochrome P450 enzymes**, including **desmolase (P450scc)**, which is crucial for **androgen synthesis** in the ovaries and adrenal glands, thereby reducing hirsutism. *1,3-beta-glucan synthase* - This enzyme is targeted by **echinocandins** (e.g., caspofungin), which inhibit **cell wall synthesis** in fungi. - **Ketoconazole** does not act on 1,3-beta-glucan synthase; its primary antifungal mechanism is inhibiting **ergosterol synthesis**. *5-alpha-reductase* - This enzyme converts **testosterone to dihydrotestosterone (DHT)**, a more potent androgen. - While 5-alpha-reductase inhibitors like **finasteride** can be used to treat hirsutism, **ketoconazole** does not primarily exert its anti-androgenic effects via this pathway. *Squalene epoxidase* - This enzyme is inhibited by **allylamines** like **terbinafine**, which are antifungal agents that disrupt **ergosterol synthesis** at an earlier step than azoles. - **Ketoconazole** inhibits 14-alpha-demethylase, a different enzyme in the ergosterol synthesis pathway. *Aromatase* - **Aromatase** converts androgens to estrogens. Inhibitors like **anastrozole** are used in breast cancer treatment to reduce estrogen levels. - While some azole antifungals can have minor effects on aromatase, it is not the primary target for ketoconazole's anti-androgenic action in treating hirsutism.

Question 26: A 25-year-old man visits a local clinic while volunteering abroad to rebuild homes after a natural disaster. He reports that he has been experiencing an intermittent rash on his feet for several weeks that is associated with occasional itching and burning. He states that he has been working in wet conditions in work boots and often does not get a chance to remove them until just before going to bed. On physical exam, there is diffuse erythema and maceration of the webspaces between his toes. He starts taking a medication. Two days later, he experiences severe nausea and vomiting after drinking alcohol. Which of the following is the mechanism of action of the drug most likely prescribed in this case?

A. Inhibition of cell wall synthesis
B. Inhibition of steroid synthesis
C. Inhibition of DNA synthesis
D. Cell arrest at metaphase
E. Disruption of fungal cell membrane
F. Cell arrest at metaphase (Correct Answer)

Explanation: ***Cell arrest at metaphase*** - The patient's clinical presentation (intermittent rash, itching, burning on feet, erythema and maceration of toe webspaces, prolonged wet conditions in work boots) is characteristic of **tinea pedis** (athlete's foot), a dermatophyte fungal infection. - The **disulfiram-like reaction** (severe nausea and vomiting after alcohol consumption) is a classic adverse effect of **griseofulvin**, an oral antifungal commonly used for dermatophyte infections including tinea pedis. - **Griseofulvin's mechanism of action**: Interferes with fungal **microtubule function** by disrupting the mitotic spindle, causing **cell cycle arrest at metaphase** and inhibiting fungal cell division. - Griseofulvin also disrupts nucleic acid synthesis and inhibits fungal mitosis, making it fungistatic against dermatophytes. *Disruption of fungal cell membrane* - This mechanism describes **azole antifungals** (ketoconazole, fluconazole, clotrimazole) which inhibit ergosterol synthesis, and **polyene antifungals** (amphotericin B, nystatin) which bind to ergosterol. - While azoles can also cause disulfiram-like reactions (particularly ketoconazole), the mechanism of cell arrest at metaphase is more specific to griseofulvin, which is the first-line oral agent for tinea pedis in many cases. - **Allylamines** (terbinafine) also disrupt the membrane by inhibiting squalene epoxidase but do not cause disulfiram-like reactions. *Inhibition of steroid synthesis* - This describes **azole antifungals** that inhibit fungal **ergosterol synthesis** (a steroid component of fungal cell membranes) by blocking 14-α-demethylase. - While ketoconazole can cause disulfiram-like reactions, the question stem points more specifically to griseofulvin given the classic presentation and reaction pattern. *Inhibition of DNA synthesis* - This mechanism describes **flucytosine** (5-FC), a pyrimidine analog that inhibits fungal DNA and RNA synthesis. - Flucytosine is used primarily for systemic mycoses (Cryptococcus, Candida) in combination with amphotericin B, not for dermatophyte infections like tinea pedis. - It does not cause disulfiram-like reactions with alcohol. *Inhibition of cell wall synthesis* - This mechanism is characteristic of **antibacterial agents** (penicillins, cephalosporins, vancomycin) that target bacterial peptidoglycan cell walls. - While fungi have cell walls made of chitin and glucans, and **echinocandins** (caspofungin, micafungin) inhibit fungal cell wall synthesis by blocking β-1,3-glucan synthase, these agents are used for invasive candidiasis and aspergillosis, not tinea pedis. - Echinocandins do not cause disulfiram-like reactions.

Question 27: A 64-year-old woman comes to the emergency room because of a sudden weakness in her right arm and leg. She has atrial fibrillation, tinea unguium, gastroesophageal reflux disease, hypertension, and hypercholesterolemia. Current medications include warfarin, enalapril, simvastatin, lansoprazole, hydrochlorothiazide, griseofulvin, and ginkgo biloba. Two weeks ago, she had an appointment with her podiatrist. Physical examination shows sagging of her right lower face and decreased muscle strength in her right upper and lower extremity. Babinski sign is positive on the right. Her prothrombin time is 14 seconds (INR = 1.5). Which of the following drugs is the most likely underlying cause of this patient's current condition?

A. Ginkgo biloba
B. Lansoprazole
C. Enalapril
D. Griseofulvin (Correct Answer)
E. Simvastatin

Explanation: ***Griseofulvin*** - Has been shown to **reduce the effectiveness of warfarin** by inducing hepatic enzymes, leading to a subtherapeutic INR and increased risk of thrombotic events like stroke. - The patient's **INR of 1.5 is subtherapeutic** for atrial fibrillation, which normally requires an INR between 2.0 and 3.0 to prevent stroke. *Ginkgo biloba* - Is known to **increase the risk of bleeding** when taken with anticoagulants like warfarin, potentially leading to a higher INR and hemorrhagic stroke. - In this case, the patient's **INR is subtherapeutic**, which points away from a bleeding diathesis caused by ginkgo biloba. *Lansoprazole* - While it can interact with warfarin, **proton pump inhibitors (PPIs)** typically **increase the INR** by inhibiting warfarin metabolism, increasing bleeding risk. - The patient's **subtherapeutic INR** makes lansoprazole less likely to be the cause of the thrombotic event. *Enalapril* - As an **ACE inhibitor**, enalapril generally has **no significant direct interaction with warfarin** that would lead to a subtherapeutic INR or increased stroke risk in this way. - It is primarily used for hypertension and heart failure, and its effects would not explain the observed subtherapeutic INR and thrombotic stroke. *Simvastatin* - Can **increase the effect of warfarin** by inhibiting its metabolism, leading to an **elevated INR** and increased bleeding risk. - The patient's **low INR** suggests that simvastatin is not the cause of the subtherapeutic anticoagulation or stroke.

Question 28: A 19-year-old woman comes to the physician because of worsening pain with swallowing for 3 days and a dry sensation in the mouth over the past week. She has a history of asthma controlled with inhaled fluticasone and albuterol. Physical examination shows white plaques on the dorsal surface of the tongue and buccal mucosa that bleed when scraped off. Which of the following is the most appropriate pharmacotherapy?

A. Amphotericin B
B. Nystatin (Correct Answer)
C. Acyclovir
D. Griseofulvin
E. Triamcinolone

Explanation: **Nystatin** - The patient's presentation with **white plaques on the dorsal surface of the tongue and buccal mucosa that bleed when scraped off**, along with a history of inhaled fluticasone use, is highly suggestive of **oral candidiasis (thrush)**. - **Nystatin** is an antifungal medication typically used as a **topical swish and swallow solution** for oral candidiasis, effectively treating localized infections with minimal systemic absorption. *Amphotericin B* - **Amphotericin B** is a potent systemic antifungal used for **severe, invasive fungal infections**, often given intravenously due to significant side effects. - It is **not the first-line treatment** for localized oral candidiasis, which is typically managed with less toxic topical agents. *Acyclovir* - **Acyclovir** is an **antiviral medication** used to treat **herpes simplex virus (HSV)** infections, such as oral herpes or cold sores. - The patient's symptoms are characteristic of a fungal infection, not a viral one. *Griseofulvin* - **Griseofulvin** is an **oral antifungal primarily used for dermatophyte infections** of the skin, hair, and nails (e.g., tinea capitis, onychomycosis). - It is ineffective against *Candida* species and therefore not appropriate for oral candidiasis. *Triamcinolone* - **Triamcinolone** is a **corticosteroid** used to reduce inflammation and is often found in topical creams or inhaled formulations. - Corticosteroids can actually **worsen fungal infections** like candidiasis by suppressing the immune response, and are therefore contraindicated.

Question 29: A 55-year-old man, who underwent a kidney transplant 2 years ago, presents in septic shock. He is compliant with his immunosuppressive therapy. He does not use any drugs and is sexually active with one male partner. His complete blood count returns as follows: Hemoglobin: 13.7 g/dL, white blood cell count: 4000 cells/microliter, platelets 250,000 cells/microliter. Of note, from his differential: neutrophils: 10%, lymphocytes: 45%, and monocytes: 7%. His basic metabolic profile is notable for a creatinine remaining at his baseline of 0.9 mg/dL. The patient is started on broad spectrum antibiotics, but his condition does not improve. Fungal blood cultures are obtained and grow Candida species. Which of the following was the most-likely predisposing factor?

A. Defective IL-2 receptor
B. HIV infection
C. Decreased phagocytic cell count (Correct Answer)
D. Renal failure
E. Failure to take suppressive trimethoprim/sulfamethoxazole therapy

Explanation: **Decreased phagocytic cell count** - The patient's **neutrophil count is 10%** of 4000 WBCs, which is 400 cells/microliter. This profound **neutropenia** is a major risk factor for fungal infections like *Candida*. - Immunosuppressive therapy post-transplant often suppresses **myeloid cell lines**, leading to a decreased phagocytic cell count and increased susceptibility to opportunistic infections. *Defective IL-2 receptor* - A defective **IL-2 receptor** would impair T-cell proliferation and function, predisposing to disseminated viral infections (e.g., CMV, EBV) or specific intracellular bacterial infections, rather than typically *Candida* fungemia. - While broad immunosuppression occurs, the direct link to *Candida* septic shock with severe neutropenia is less direct than a primary phagocytic defect. *HIV infection* - HIV infection causes **CD4+ T-cell depletion**, leading to susceptibility to various opportunistic infections, including *Candida* (especially oral/esophageal). However, the patient's lymphocyte count (45%) is not critically low, and the primary issue here is severe neutropenia, which HIV does not directly cause to this extent. - The patient also reports being sexually active with one male partner but does not use drugs and the complete blood count (CBC) does not show direct signs of HIV-related immune deficiency such as extremely low lymphocyte counts. *Renal failure* - The patient's **creatinine is at baseline (0.9 mg/dL)**, indicating that his transplanted kidney is functioning well and he is not in renal failure. - While chronic kidney disease can cause some immune dysfunction, acute renal failure is not present and cannot be the predisposing factor here. *Failure to take suppressive trimethoprim/sulfamethoxazole therapy* - **Trimethoprim/sulfamethoxazole (TMP/SMX)** is primarily prophylactic against *Pneumocystis jirovecii* pneumonia and certain bacterial infections, not typically systemic fungal infections like *Candida* septicemia. - Although broad-spectrum, its main role is not preventing disseminated candidemia, especially in a severely neutropenic patient.

Question 30: A 57-year-old florist presents to his family physician with nodular lesions on his right hand and forearm. He explains that he got pricked by a rose thorn on his right "pointer finger" where the first lesions appeared, and the other lesions then began to appear in an ascending manner. The physician prescribed a medication and warned him of gynecomastia as a side effect if taken for long periods of time. Which of the following is the mechanism of action of the medication?

A. Inhibits squalene epoxidase
B. Binds to ergosterol, forming destructive pores in cell membrane
C. Disrupts microtubule function
D. Inhibits ergosterol synthesis (Correct Answer)
E. Inhibits formation of beta glucan

Explanation: ***Inhibits ergosterol synthesis*** - The clinical presentation of **nodular lesions** on the hand and forearm in an **ascending manner** after a rose thorn prick is characteristic of **sporotrichosis**, caused by *Sporothrix schenckii*. - **Itraconazole** is the treatment of choice for sporotrichosis, and it works by **inhibiting ergosterol synthesis** via the inhibition of **lanosterol 14-alpha-demethylase**. Gynecomastia is a known side effect of long-term itraconazole use. *Inhibits squalene epoxidase* - This is the mechanism of action of **terbinafine**, another antifungal agent. - While terbinafine is used for some fungal infections, it is **not the first-line treatment for sporotrichosis** and is not typically associated with gynecomastia as a common side effect. *Binds to ergosterol, forming destructive pores in cell membrane* - This describes the mechanism of action of **amphotericin B** and **nystatin**. - Amphotericin B is used for severe systemic fungal infections, but sporotrichosis typically responds well to oral itraconazole, and amphotericin B is reserved for severe or disseminated cases. *Disrupts microtubule function* - This is the mechanism of action of **griseofulvin**, an antifungal agent primarily used for dermatophyte infections of the skin, hair, and nails. - It is **not effective against *Sporothrix schenckii*** and is not associated with the clinical scenario described. *Inhibits formation of beta glucan* - This is the mechanism of action of **echinocandins** (e.g., caspofungin, micafungin, anidulafungin). - Echinocandins are effective against *Candida* and *Aspergillus* species but have **limited activity against dimorphic fungi** like *Sporothrix schenckii*.

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Polyenes (amphotericin formulations)

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Azoles (imidazoles and triazoles)

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Echinocandins

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Flucytosine

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Griseofulvin

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Terbinafine

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Topical antifungal agents

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Antifungal prophylaxis protocols

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Antifungal spectrum of activity

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Antifungal resistance mechanisms

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Antifungal therapeutic drug monitoring

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Drug interactions with antifungals

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Treatment guidelines for invasive fungal infections

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