A 54-year-old man electively underwent an open cholecystectomy for cholelithiasis. The procedure was performed under general anesthesia with inhaled anesthetic agents, including nitrous oxide, after induction with an intravenous agent. The surgeon operated quickly, and the procedure was uncomplicated. As the surgery ended, the anesthesia resident stopped the anesthesia and noticed the oxygen saturation gradually decreasing to 84%. He quickly administers 100% oxygen, and the hypoxia improves. Which of the following most likely accounts for the decreased oxygen saturation seen after the anesthesia was stopped in this patient?
Q692
A previously healthy 32-year-old man comes to the physician because of a 2-month history of fatigue and daytime sleepiness. He works as an accountant and cannot concentrate at work anymore. He also has depressed mood and no longer takes pleasure in activities he used to enjoy, such as playing tennis with his friends. He has decreased appetite and has had a 4-kg (8.8-lb) weight loss of over the past 2 months. He does not have suicidal ideation. He is diagnosed with major depressive disorder and treatment with paroxetine is begun. The patient is at greatest risk for which of the following adverse effects?
Q693
A 60-year-old man is brought to the emergency room because of fever and increasing confusion for the past 2 days. He has paranoid schizophrenia and hypertension. His current medications are chlorpromazine and amlodipine. He appears ill. He is not oriented to time, place, or person. His temperature is 40°C (104°F), pulse is 130/min, respirations are 29/min and blood pressure is 155/100 mm Hg. Examination shows diaphoresis. Muscle tone is increased bilaterally. Deep tendon reflexes are 1+ bilaterally. Neurologic examination shows psychomotor agitation. His speech is incoherent. Lungs are clear to auscultation. His neck is supple. The abdomen is soft and nontender. Serum laboratory analysis shows a leukocyte count of 11,300/mm3 and serum creatine kinase concentration of 833 U/L. Which of the following is the most appropriate initial pharmacotherapy?
Q694
A 42-year-old man is brought to the emergency department after having a seizure. His wife states that the patient has been struggling with alcohol abuse and has recently decided to "quit once and for all". Physical exam is notable for a malnourished patient responsive to verbal stimuli. He has moderate extremity weakness, occasional palpitations, and brisk deep tendon reflexes (DTRs). EKG demonstrates normal sinus rhythm and a prolonged QT interval. What nutritional deficiency most likely contributed to these findings?
Q695
A 65-year-old woman with COPD comes to the emergency department with 2-day history of worsening shortness of breath and cough. She often has a mild productive cough, but she noticed that her sputum is more yellow than usual. She has not had any recent fevers, chills, sore throat, or a runny nose. Her only medication is a salmeterol inhaler that she uses twice daily. Her temperature is 36.7°C (98°F), pulse is 104/min, blood pressure is 134/73 mm Hg, respiratory rate is 22/min, and oxygen saturation is 85%. She appears uncomfortable and shows labored breathing. Lung auscultation reveals coarse bibasilar inspiratory crackles. A plain film of the chest shows mild hyperinflation and flattening of the diaphragm but no consolidation. She is started on supplemental oxygen via nasal cannula. Which of the following is the most appropriate initial pharmacotherapy?
Q696
A 3-year-old boy is brought to the emergency department because of worsening pain and swelling in both of his hands for 1 week. He appears distressed. His temperature is 38.5°C (101.4°F). Examination shows erythema, swelling, warmth, and tenderness on the dorsum of his hands. His hemoglobin concentration is 9.1 g/dL. A peripheral blood smear is shown. The drug indicated to prevent recurrence of this patient's symptoms is also used to treat which of the following conditions?
Q697
A 48-year-old man with a long history of mild persistent asthma on daily fluticasone therapy has been using his albuterol inhaler every day for the past month and presents requesting a refill. He denies any recent upper respiratory infections, but he says he has felt much more short of breath throughout this time frame. He works as a landscaper, and he informs you that he has been taking longer to complete some of his daily activities on the job. 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 exam reveals mild bilateral wheezes and normal heart sounds. What changes should be made to his current regimen?
Q698
A 28-year-old man visits his physician complaining of hematochezia over the last several days. He also has tenesmus and bowel urgency without any abdominal pain. He has had several milder episodes over the past several years that resolved on their own. He has no history of a serious illness and takes no medications. His blood pressure is 129/85 mm Hg; temperature, 37.4°C (99.3°F); and pulse, 75/min. On physical exam, his abdominal examination shows mild tenderness on deep palpation of the left lower quadrant. Digital rectal examination reveals anal tenderness and fresh blood. Stool examination is negative for pathogenic bacteria and an ova and parasite test is negative. Erythrocyte sedimentation rate is 28 mm/h. Colonoscopy shows diffuse erythema involving the rectum and extending to the distal sigmoid. The mucosa also shows a decreased vascular pattern with fine granularity. The remaining colon and distal ileum are normal. Biopsy of the inflamed mucosa of the sigmoid colon shows distorted crypt architecture. The most appropriate next step is to administer which of the following?
Q699
A 73-year-old man presents to his primary care physician with chest pain. He noticed the pain after walking several blocks, and the pain is relieved by sitting. On exam, he has a BP 155/89 mmHg, HR 79 bpm, and T 98.9 F. The physician refers the patient to a cardiologist and offers prescriptions for carvedilol and nitroglycerin. Which of the following describes the mechanism or effects of each of these medications, respectively?
Q700
A 33-year-old woman comes to the physician for a follow-up examination. She has a history of Crohn disease, for which she takes methotrexate. She and her husband would like to start trying to have a child. Because of the teratogenicity of methotrexate, the physician switches the patient from methotrexate to a purine analog drug that inhibits lymphocyte proliferation by blocking nucleotide synthesis. Toxicity of the newly prescribed purine analog would most likely increase if the patient was also being treated with which of the following medications?
Autonomic/CV Drugs US Medical PG Practice Questions and MCQs
Question 691: A 54-year-old man electively underwent an open cholecystectomy for cholelithiasis. The procedure was performed under general anesthesia with inhaled anesthetic agents, including nitrous oxide, after induction with an intravenous agent. The surgeon operated quickly, and the procedure was uncomplicated. As the surgery ended, the anesthesia resident stopped the anesthesia and noticed the oxygen saturation gradually decreasing to 84%. He quickly administers 100% oxygen, and the hypoxia improves. Which of the following most likely accounts for the decreased oxygen saturation seen after the anesthesia was stopped in this patient?
A. Diffusion hypoxia (Correct Answer)
B. Cardiotoxicity
C. Laryngospasm
D. Second gas effect
E. Pneumothorax
Explanation: ***Diffusion hypoxia***
- Following the cessation of **nitrous oxide** administration, a large volume of N2O rapidly diffuses from the blood into the alveoli, diluting the partial pressures of oxygen and carbon dioxide.
- This dilution can lead to a transient decrease in the partial pressure of alveolar oxygen, resulting in **hypoxia**, which resolves with 100% oxygen administration.
*Cardiotoxicity*
- While some anesthetic agents can be cardiotoxic, the rapid onset and resolution of hypoxia with oxygen administration in this scenario are not typical presentations of **anesthetic-induced cardiotoxicity**, which usually manifests with arrhythmias or myocardial dysfunction.
*Laryngospasm*
- **Laryngospasm** would cause sudden and severe airway obstruction, often accompanied by stridor and difficulty ventilating, which is a more acute and dramatic event than the described gradual decrease in oxygen saturation.
- While it can cause hypoxia, the prompt improvement with 100% oxygen without specific maneuvers to relieve airway obstruction makes it less likely.
*Second gas effect*
- The **second gas effect** refers to the phenomenon where the rapid uptake of a highly soluble gas (like nitrous oxide) increases the alveolar concentration and thus the rate of uptake of a co-administered less soluble gas.
- This effect occurs during the *induction* phase, not upon the *cessation* of anesthesia, and it enhances rather than diminishes oxygen uptake.
*Pneumothorax*
- A **pneumothorax** would typically present with a sudden drop in oxygen saturation, often accompanied by respiratory distress, unilateral breath sounds, and potentially hemodynamic instability.
- It would not usually resolve simply by administering 100% oxygen without addressing the underlying lung collapse.
Question 692: A previously healthy 32-year-old man comes to the physician because of a 2-month history of fatigue and daytime sleepiness. He works as an accountant and cannot concentrate at work anymore. He also has depressed mood and no longer takes pleasure in activities he used to enjoy, such as playing tennis with his friends. He has decreased appetite and has had a 4-kg (8.8-lb) weight loss of over the past 2 months. He does not have suicidal ideation. He is diagnosed with major depressive disorder and treatment with paroxetine is begun. The patient is at greatest risk for which of the following adverse effects?
A. Priapism
B. Decreased libido (Correct Answer)
C. Increased suicidality
D. Postural hypotension
E. Urinary retention
Explanation: ***Decreased libido***
- **Paroxetine** is a **selective serotonin reuptake inhibitor (SSRI)**, and sexual dysfunction, including **decreased libido**, **anorgasmia**, and **erectile dysfunction**, is the **most common adverse effect** impacting 40-70% of individuals.
- This adverse effect is often a reason for **non-adherence** to antidepressant treatment and represents the **greatest risk** among the listed options.
*Priapism*
- **Priapism** (a prolonged, painful erection) is a rare but serious side effect more commonly associated with **trazodone**, an antidepressant with **α1-adrenergic receptor blockade** properties.
- It is not a typical adverse effect of SSRIs like paroxetine.
*Increased suicidality*
- While there is a **black box warning** for increased suicidality in children, adolescents, and young adults (**up to age 24**) when starting antidepressants, this patient is **32 years old**.
- The risk of increased suicidality **decreases with age** and is **lowest in adults over 25**, making this a less likely adverse effect than sexual dysfunction in this patient.
*Postural hypotension*
- **Postural hypotension** is more common with antidepressants that have **alpha-1 adrenergic blocking effects**, such as tricyclic antidepressants (TCAs) and some atypical antidepressants like trazodone.
- SSRIs like paroxetine generally have a **much lower incidence** of alpha-adrenergic side effects.
*Urinary retention*
- **Urinary retention** is primarily an **anticholinergic side effect**, commonly seen with tricyclic antidepressants (TCAs).
- While paroxetine has the **highest anticholinergic activity among SSRIs**, it is still **significantly lower than TCAs**, making urinary retention an **uncommon adverse effect** and far less likely than sexual dysfunction.
Question 693: A 60-year-old man is brought to the emergency room because of fever and increasing confusion for the past 2 days. He has paranoid schizophrenia and hypertension. His current medications are chlorpromazine and amlodipine. He appears ill. He is not oriented to time, place, or person. His temperature is 40°C (104°F), pulse is 130/min, respirations are 29/min and blood pressure is 155/100 mm Hg. Examination shows diaphoresis. Muscle tone is increased bilaterally. Deep tendon reflexes are 1+ bilaterally. Neurologic examination shows psychomotor agitation. His speech is incoherent. Lungs are clear to auscultation. His neck is supple. The abdomen is soft and nontender. Serum laboratory analysis shows a leukocyte count of 11,300/mm3 and serum creatine kinase concentration of 833 U/L. Which of the following is the most appropriate initial pharmacotherapy?
A. Cyproheptadine
B. Dantrolene (Correct Answer)
C. Physostigmine
D. Propranolol
E. Clozapine
Explanation: ***Dantrolene***
- The patient's presentation with **fever (40°C), muscle rigidity, altered mental status, and elevated creatine kinase** while on **chlorpromazine** is highly suggestive of **neuroleptic malignant syndrome (NMS)**.
- **Dantrolene** is a direct-acting skeletal muscle relaxant used to treat the muscle rigidity, hyperthermia, and rhabdomyolysis associated with NMS.
*Cyproheptadine*
- **Cyproheptadine** is a serotonin antagonist used to treat **serotonin syndrome**, which shares some features with NMS but is typically associated with serotonergic agents.
- While there's some overlap, NMS is primarily due to dopamine blockade, and cyproheptadine is not the first-line treatment.
*Physostigmine*
- **Physostigmine** is an acetylcholinesterase inhibitor used to reverse **anticholinergic toxicity**.
- The patient's symptoms are not indicative of anticholinergic toxicity; rather, they point to a dopaminergic blockade.
*Propranolol*
- **Propranolol** is a non-selective beta-blocker that can be used to manage some of the **autonomic instability** (e.g., tachycardia, hypertension) in NMS.
- However, it does not address the underlying muscle rigidity or hyperthermia, which are critical components requiring specific treatment like dantrolene.
*Clozapine*
- **Clozapine** is an atypical antipsychotic often used for refractory schizophrenia, but it is not a treatment for NMS.
- In fact, antipsychotics are the causative agents of NMS, and continuing or initiating another antipsychotic would be contraindicated.
Question 694: A 42-year-old man is brought to the emergency department after having a seizure. His wife states that the patient has been struggling with alcohol abuse and has recently decided to "quit once and for all". Physical exam is notable for a malnourished patient responsive to verbal stimuli. He has moderate extremity weakness, occasional palpitations, and brisk deep tendon reflexes (DTRs). EKG demonstrates normal sinus rhythm and a prolonged QT interval. What nutritional deficiency most likely contributed to these findings?
A. Vitamin D
B. Magnesium (Correct Answer)
C. Potassium
D. Calcium
E. Folate
Explanation: ***Magnesium***
- **Hypomagnesemia** is common in chronic alcoholics due to poor nutrition and increased renal loss, leading to neuromuscular excitability (seizures, hyperreflexia, weakness) and cardiac abnormalities (prolonged QT interval, palpitations).
- Magnesium is a crucial cofactor for many enzymes and plays a vital role in nerve impulse transmission, muscle contraction, and maintaining cardiac rhythm.
*Vitamin D*
- **Vitamin D deficiency** is associated with bone demineralization (osteomalacia) and weakness, but it does not typically cause acute seizures, prolonged QT interval, or brisk deep tendon reflexes.
- While chronic alcohol abuse can impair vitamin D metabolism, the acute presentation here points more strongly to electrolyte imbalances.
*Potassium*
- **Hypokalemia** can cause muscle weakness, fatigue, and cardiac arrhythmias, including a prolonged QT interval, but it usually leads to **diminished** or absent DTRs, not brisk DTRs.
- Seizures are also not a primary manifestation of hypokalemia.
*Calcium*
- **Hypocalcemia** can cause muscle cramps, spasms, and seizures due to increased neuromuscular excitability, and it can also lead to a prolonged QT interval.
- However, brisk deep tendon reflexes (hyperreflexia) are more characteristic of **hypomagnesemia** that often coexists with hypocalcemia because magnesium is required for **parathyroid hormone (PTH)** secretion and action.
*Folate*
- **Folate deficiency** in alcoholics primarily causes **macrocytic anemia** and can lead to neurological symptoms like peripheral neuropathy or cognitive impairment.
- It does not explain the acute seizure, prolonged QT, brisk DTRs, or palpitations seen in this patient.
Question 695: A 65-year-old woman with COPD comes to the emergency department with 2-day history of worsening shortness of breath and cough. She often has a mild productive cough, but she noticed that her sputum is more yellow than usual. She has not had any recent fevers, chills, sore throat, or a runny nose. Her only medication is a salmeterol inhaler that she uses twice daily. Her temperature is 36.7°C (98°F), pulse is 104/min, blood pressure is 134/73 mm Hg, respiratory rate is 22/min, and oxygen saturation is 85%. She appears uncomfortable and shows labored breathing. Lung auscultation reveals coarse bibasilar inspiratory crackles. A plain film of the chest shows mild hyperinflation and flattening of the diaphragm but no consolidation. She is started on supplemental oxygen via nasal cannula. Which of the following is the most appropriate initial pharmacotherapy?
A. Albuterol and montelukast
B. Albuterol and theophylline
C. Prednisone and albuterol (Correct Answer)
D. Roflumilast and prednisone
E. Prednisone and salmeterol
Explanation: ***Prednisone and albuterol***
- This patient is experiencing an **acute exacerbation of COPD** (AECOPD) characterized by worsening dyspnea, increased sputum purulence (yellow sputum), and elevated respiratory rate, despite no fever or chills. AECOPD is managed with **systemic corticosteroids** (like prednisone) and **short-acting bronchodilators** (like albuterol).
- Prednisone reduces **airway inflammation**, while albuterol provides rapid **bronchodilation** to relieve bronchospasm and improve airflow.
*Albuterol and montelukast*
- **Montelukast** is a leukotriene receptor antagonist used for chronic asthma management and sometimes for COPD patients with an asthmatic component, but it is not a first-line agent for acute exacerbations.
- While **albuterol** is appropriate, montelukast works too slowly to be the primary acute anti-inflammatory agent needed for an AECOPD.
*Albuterol and theophylline*
- **Theophylline** is a phosphodiesterase inhibitor that can improve lung function but has a narrow therapeutic index and significant side effects, making it a less preferred option, especially in acute settings.
- While **albuterol** is appropriate, theophylline is not generally used as an initial agent for AECOPD given safer and more effective alternatives like corticosteroids.
*Roflumilast and prednisone*
- **Roflumilast** is a phosphodiesterase-4 inhibitor used to reduce exacerbations in patients with severe COPD and chronic bronchitis, but it is a chronic medication and not indicated for acute management.
- While **prednisone** is appropriate, roflumilast is not an acute bronchodilator for immediate relief.
*Prednisone and salmeterol*
- **Salmeterol** is a **long-acting beta-agonist (LABA)**, which is part of the patient's maintenance therapy for COPD. In an acute exacerbation, **short-acting bronchodilators** like albuterol are preferred for rapid relief.
- While **prednisone** is appropriate, continuing salmeterol alone as the bronchodilator in an acute setting is insufficient without a short-acting agent.
Question 696: A 3-year-old boy is brought to the emergency department because of worsening pain and swelling in both of his hands for 1 week. He appears distressed. His temperature is 38.5°C (101.4°F). Examination shows erythema, swelling, warmth, and tenderness on the dorsum of his hands. His hemoglobin concentration is 9.1 g/dL. A peripheral blood smear is shown. The drug indicated to prevent recurrence of this patient's symptoms is also used to treat which of the following conditions?
A. Chronic kidney disease
B. Megaloblastic anemia
C. Primary syphilis
D. Polycythemia vera (Correct Answer)
E. Iron intoxication
Explanation: ***Polycythemia vera***
- The patient presents with **dactylitis**, a common manifestation of **sickle cell disease** in children, characterized by swelling and pain in the hands or feet due to vaso-occlusion. The peripheral blood smear shows **sickled red blood cells**. **Hydroxyurea** is the indicated drug for preventing recurrence of symptoms in sickle cell disease, and it is also used to treat **polycythemia vera** by reducing red blood cell production.
- **Hydroxyurea** increases the production of **fetal hemoglobin (HbF)**, which interferes with the sickling process, and also has myelosuppressive effects used in myeloproliferative neoplasms like polycythemia vera.
*Chronic kidney disease*
- While chronic kidney disease can cause **anemia** (typically normocytic, normochromic), it is not associated with **sickle cell crisis** or its treatment, hydroxyurea.
- **Erythropoietin-stimulating agents** are typically used to manage anemia in chronic kidney disease, not hydroxyurea.
*Megaloblastic anemia*
- **Megaloblastic anemia** is characterized by large, immature red blood cells and caused by deficiencies in **vitamin B12 or folate**.
- Treatment involves supplementing the deficient vitamin, not hydroxyurea, which is a myelosuppressive agent.
*Primary syphilis*
- **Primary syphilis** is a sexually transmitted infection caused by *Treponema pallidum*, presenting with a **chancre**.
- Treatment is typically with **penicillin**, and has no association with sickle cell disease or hydroxyurea.
*Iron intoxication*
- **Iron intoxication** results from excessive iron intake, leading to gastrointestinal symptoms, metabolic acidosis, and organ damage.
- Treatment involves **chelation therapy** with deferoxamine, not hydroxyurea, which has a different pharmacological mechanism.
Question 697: A 48-year-old man with a long history of mild persistent asthma on daily fluticasone therapy has been using his albuterol inhaler every day for the past month and presents requesting a refill. He denies any recent upper respiratory infections, but he says he has felt much more short of breath throughout this time frame. He works as a landscaper, and he informs you that he has been taking longer to complete some of his daily activities on the job. 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 exam reveals mild bilateral wheezes and normal heart sounds. What changes should be made to his current regimen?
A. Add ciclesonide to current regimen
B. Discontinue fluticasone and instead use salmeterol
C. Add salmeterol to current regimen (Correct Answer)
D. Add cromolyn to current regimen
E. Discontinue fluticasone and add ipratropium to current regimen
Explanation: ***Add salmeterol to current regimen***
- The patient's increased albuterol use and worsening symptoms despite daily **fluticasone** indicate an escalation in his asthma severity, moving him from mild persistent to moderate persistent asthma.
- Adding a **long-acting beta-agonist (LABA)** like **salmeterol** to his inhaled corticosteroid (fluticasone) is the next step in therapy for moderate persistent asthma to achieve better symptom control.
*Add ciclesonide to current regimen*
- **Ciclesonide** is another **inhaled corticosteroid (ICS)**. Adding it would either replace or supplement **fluticasone**, which would not address the need for an additional class of medication to improve bronchodilation and reduce rescue inhaler use.
- The primary issue is insufficient disease control with current ICS, not a preference for a different steroid.
*Discontinue fluticasone and instead use salmeterol*
- **Discontinuing fluticasone** (an ICS) would remove the foundational anti-inflammatory therapy for asthma, which is critical for long-term control.
- While **salmeterol** (a LABA) helps with bronchodilation, using it as monotherapy without an ICS is associated with an increased risk of severe asthma exacerbations and is not recommended.
*Add cromolyn to current regimen*
- **Cromolyn sodium** is a mast cell stabilizer used to prevent asthma symptoms, often in mild cases or for exercise-induced asthma.
- It is generally less potent than ICS and LABA combinations and would not be sufficient for a patient whose asthma is worsening despite daily ICS therapy.
*Discontinue fluticasone and add ipratropium to current regimen*
- **Discontinuing fluticasone** would remove necessary anti-inflammatory control.
- **Ipratropium** is a short-acting anticholinergic often used in acute asthma exacerbations or in patients who cannot tolerate beta-agonists, but it is not a first-line daily maintenance therapy for moderate persistent asthma.
Question 698: A 28-year-old man visits his physician complaining of hematochezia over the last several days. He also has tenesmus and bowel urgency without any abdominal pain. He has had several milder episodes over the past several years that resolved on their own. He has no history of a serious illness and takes no medications. His blood pressure is 129/85 mm Hg; temperature, 37.4°C (99.3°F); and pulse, 75/min. On physical exam, his abdominal examination shows mild tenderness on deep palpation of the left lower quadrant. Digital rectal examination reveals anal tenderness and fresh blood. Stool examination is negative for pathogenic bacteria and an ova and parasite test is negative. Erythrocyte sedimentation rate is 28 mm/h. Colonoscopy shows diffuse erythema involving the rectum and extending to the distal sigmoid. The mucosa also shows a decreased vascular pattern with fine granularity. The remaining colon and distal ileum are normal. Biopsy of the inflamed mucosa of the sigmoid colon shows distorted crypt architecture. The most appropriate next step is to administer which of the following?
A. Ciprofloxacin
B. Mesalamine (Correct Answer)
C. Azathioprine
D. Metronidazole
E. Total parenteral nutrition
Explanation: ***Mesalamine***
- This patient presents with symptoms and endoscopic findings consistent with **ulcerative colitis**, specifically **proctosigmoiditis** (inflammation limited to the rectum and distal sigmoid).
- **Mesalamine** (an aminosalicylate) is the first-line treatment for inducing and maintaining remission in mild-to-moderate ulcerative colitis, especially when it is localized to the distal colon.
*Ciprofloxacin*
- **Ciprofloxacin** is an antibiotic and would be considered if there was suspicion of **bacterial infection** or severe, complicated inflammatory bowel disease with signs of infection.
- The stool tests were negative for pathogenic bacteria, making an antibiotic unlikely as a primary treatment for this presentation.
*Azathioprine*
- **Azathioprine** is an immunosuppressant used for **moderate-to-severe ulcerative colitis** or when patients are refractory to conventional therapy like mesalamine or corticosteroids.
- This patient has a milder presentation, with localized disease and current treatment not yet initiated, meaning azathioprine is a step too far.
*Metronidazole*
- **Metronidazole** is an antibiotic often used for anaerobic infections or in certain cases of Crohn's disease (e.g., peri-anal disease), but not typically as first-line for ulcerative colitis.
- No clear indication of bacterial overgrowth or abscess is present, and stool tests were negative.
*Total parenteral nutrition*
- **Total parenteral nutrition (TPN)** is reserved for patients with severe malnutrition, intractable vomiting, or conditions preventing enteral feeding.
- This patient does not exhibit signs of severe malnutrition or an inability to tolerate oral intake, making TPN unnecessary and overly aggressive.
Question 699: A 73-year-old man presents to his primary care physician with chest pain. He noticed the pain after walking several blocks, and the pain is relieved by sitting. On exam, he has a BP 155/89 mmHg, HR 79 bpm, and T 98.9 F. The physician refers the patient to a cardiologist and offers prescriptions for carvedilol and nitroglycerin. Which of the following describes the mechanism or effects of each of these medications, respectively?
A. Increased contractility; Decreased endothelial nitric oxide
B. Decreased cAMP; Increased cGMP (Correct Answer)
C. Increased cAMP; Increased cAMP
D. Decreased cGMP; Increased venous resistance
E. Increased heart rate; Decreased arterial resistance
Explanation: ***Decreased cAMP; Increased cGMP***
- **Carvedilol** is a beta-blocker that *blocks β1 and β2 adrenergic receptors*, leading to a **decrease in intracellular cAMP**, which in turn reduces heart rate, contractility, and blood pressure.
- **Nitroglycerin** acts by releasing **nitric oxide**, which activates **guanylate cyclase** to convert GTP to **cGMP**, leading to smooth muscle relaxation and vasodilation.
*Increased contractility; Decreased endothelial nitric oxide*
- **Carvedilol** (a beta-blocker) causes a **decrease in contractility**, not an increase, by blocking beta-adrenergic receptors.
- **Nitroglycerin** works by **increasing** the production of nitric oxide, not decreasing it.
*Increased cAMP; Increased cAMP*
- **Carvedilol** (a beta-blocker) functions by **decreasing** cAMP, not increasing it.
- While other agents might increase cAMP, this is not the mechanism for nitroglycerin.
*Decreased cGMP; Increased venous resistance*
- **Nitroglycerin** works by **increasing cGMP**, which promotes vasodilation, rather than decreasing it.
- Nitroglycerin causes **decreased venous resistance** (venous dilation) to reduce preload, not increased resistance.
*Increased heart rate; Decreased arterial resistance*
- **Carvedilol** (a beta-blocker) primarily **decreases heart rate**, not increases it.
- While nitroglycerin does cause some arterial dilation, its primary effect at therapeutic doses is **venous dilation** to reduce preload, not just decreased arterial resistance.
Question 700: A 33-year-old woman comes to the physician for a follow-up examination. She has a history of Crohn disease, for which she takes methotrexate. She and her husband would like to start trying to have a child. Because of the teratogenicity of methotrexate, the physician switches the patient from methotrexate to a purine analog drug that inhibits lymphocyte proliferation by blocking nucleotide synthesis. Toxicity of the newly prescribed purine analog would most likely increase if the patient was also being treated with which of the following medications?
A. Hydroxyurea
B. Febuxostat (Correct Answer)
C. Pemetrexed
D. Cyclosporine
E. Rasburicase
Explanation: ***Febuxostat***
- Febuxostat is a **xanthine oxidase inhibitor**, which will therefore increase the levels of the purine analog, as the purine analog is metabolized by **xanthine oxidase**.
- Elevated levels of purine analogs can lead to increased toxicity, particularly **myelosuppression**.
*Hydroxyurea*
- Hydroxyurea inhibits **ribonucleotide reductase**, affecting DNA synthesis and repair.
- Its mechanism of action is distinct from purine analog metabolism via xanthine oxidase, thus it is unlikely to directly increase purine analog toxicity through altered metabolism.
*Pemetrexed*
- Pemetrexed is an **antifolate agent** that inhibits several folate-dependent enzymes involved in pyrimidine and purine synthesis.
- While it affects nucleotide synthesis, it is not primarily metabolized by xanthine oxidase, nor does it inhibit xanthine oxidase to alter purine analog levels.
*Cyclosporine*
- Cyclosporine is a **calcineurin inhibitor** used as an immunosuppressant, primarily by inhibiting T-lymphocyte activation.
- It does not directly interact with the metabolic pathways of purine analogs in a way that would significantly increase their toxicity.
*Rasburicase*
- Rasburicase is a recombinant **urate oxidase** enzyme that converts uric acid to allantoin, used to manage tumor lysis syndrome.
- It works on uric acid metabolism and does not inhibit xanthine oxidase, so it would not increase the toxicity of the purine analog.
