Clinical Pharmacology — MCQs
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A 50-year-old female with rheumatoid arthritis is being considered for infliximab therapy. Which of the following tests should be performed before beginning treatment?
A 14-year-old presented with recurrent epistaxis along with characteristic skin and mucous membrane lesions. The lesions were seen at the dorsum of the tongue, oral cavity, buccal mucosa, lips, palate, and nasal mucosa. Lab findings revealed a normal coagulation profile. Which of the following drugs has been recently approved for this condition?
A diabetic patient with Enterococcus faecalis sepsis, on intravenous Linezolid, developed high anion gap metabolic acidosis with increased serum lactate and negative ketones. What is the most probable acid-base abnormality?
Which of the following is NOT a cause of hyperkalemia?
A 46-year-old male presented to the emergency with muscle weakness and cramping. He has been taking hydrochlorothiazide for recently diagnosed hypertension. Which of the following is the most likely cause of his symptoms?
Immediately after eating, a man develops swelling of face and lips, respiratory distress, intense pruritus, hypotension, and a feeling of impending doom. What is the most likely diagnosis?
Which of the following medications can cause erectile dysfunction?
HLA-B*1502 is a genetic marker for which of the following conditions?
A young female presents with severe abdominal pain, constipation, irrelevant talking, a BP of 160/110 mmHg, heart rate of 120/min, fever, and a positive Watson-Schwartz test in urine. Which of the following drugs should not be used in this condition?
Testing of HLA-B57:07 is recommended prior to the initiation of which of the following anti-retroviral agents?
Clinical Pharmacology Indian Medical PG Practice Questions and MCQs
Question 11: A 50-year-old female with rheumatoid arthritis is being considered for infliximab therapy. Which of the following tests should be performed before beginning treatment?
- A. Liver function tests
- B. PPD skin test (Correct Answer)
- C. Pulmonary function tests
- D. Visual examination
Explanation: **Explanation:** **Infliximab** is a chimeric monoclonal antibody that inhibits **Tumor Necrosis Factor-alpha (TNF-α)**. TNF-α plays a critical role in the immune system's ability to form and maintain **granulomas**, which sequester *Mycobacterium tuberculosis*. 1. **Why the PPD skin test is correct:** By inhibiting TNF-α, infliximab can cause the breakdown of existing granulomas [1], leading to the **reactivation of Latent Tuberculosis Infection (LTBI)**. This can result in severe, disseminated, or miliary tuberculosis. Therefore, all patients must be screened for TB using a PPD (Tuberculin) skin test or an Interferon-Gamma Release Assay (IGRA) [2] and a chest X-ray before initiating therapy. If LTBI is detected, prophylactic treatment (e.g., Isoniazid) must be started before the biologic. 2. **Why other options are incorrect:** * **Liver Function Tests (A):** While some biologics can cause hepatotoxicity, they are not the primary mandatory screening requirement compared to TB screening. * **Pulmonary Function Tests (C):** These are typically required for drugs causing interstitial lung disease, such as **Methotrexate** [1] or **Amiodarone**, but not routinely for Infliximab. * **Visual Examination (D):** This is mandatory for patients starting **Hydroxychloroquine** (to monitor for bull’s eye maculopathy) or **Ethambutol**, but not for TNF inhibitors. **NEET-PG High-Yield Pearls:** * **TNF-α Inhibitors:** Include Infliximab, Adalimumab, and Etanercept [1]. * **Contraindications:** Avoid TNF inhibitors in patients with **NYHA Class III/IV Heart Failure** (can worsen outcomes) and active infections. * **Screening:** Always screen for **Hepatitis B** and **TB** before starting any biologic DMARD. * **Vaccination:** Live vaccines are contraindicated while on TNF-inhibitor therapy.
Question 12: A 14-year-old presented with recurrent epistaxis along with characteristic skin and mucous membrane lesions. The lesions were seen at the dorsum of the tongue, oral cavity, buccal mucosa, lips, palate, and nasal mucosa. Lab findings revealed a normal coagulation profile. Which of the following drugs has been recently approved for this condition?
- A. Bevacizumab (Correct Answer)
- B. Ranibizumab
- C. Transtuzumab
- D. Sorafenib
Explanation: ### Explanation **Diagnosis: Hereditary Hemorrhagic Telangiectasia (HHT) / Osler-Weber-Rendu Syndrome** The clinical presentation of recurrent epistaxis, characteristic telangiectasias on the tongue, lips, and oral mucosa, and a normal coagulation profile is diagnostic of **Hereditary Hemorrhagic Telangiectasia (HHT)** [1], [2]. HHT is an autosomal dominant disorder characterized by vascular malformations (AVMs) and angiodysplasia. **1. Why Bevacizumab is Correct:** The underlying pathophysiology of HHT involves the over-expression of **Vascular Endothelial Growth Factor (VEGF)**, which leads to fragile, disorganized vessel formation. **Bevacizumab** is a humanized monoclonal antibody that inhibits VEGF. Recent clinical trials and guidelines (including International HHT Guidelines) have approved its use (off-label but standard of care) for reducing the frequency and severity of epistaxis and managing high-output heart failure caused by hepatic AVMs in HHT patients. **2. Analysis of Incorrect Options:** * **Ranibizumab:** While also an anti-VEGF agent, it is a monoclonal antibody fragment primarily used via intravitreal injection for ophthalmological conditions like wet AMD and macular edema. It is not used systemically for HHT. * **Trastuzumab:** A monoclonal antibody targeting the **HER2/neu** receptor. It is used in HER2-positive breast and gastric cancers, having no role in vascular malformations. * **Sorafenib:** A multikinase inhibitor (targeting Raf, VEGF-R, and PDGF-R) used primarily for Hepatocellular Carcinoma (HCC) and Renal Cell Carcinoma (RCC). It is not the drug of choice for HHT. **3. Clinical Pearls for NEET-PG:** * **Inheritance:** Autosomal Dominant [1]. * **Triad:** Epistaxis, Telangiectasias, and Family History. * **Curacao Criteria:** Used for diagnosis (Epistaxis, Telangiectasia, Visceral lesions, First-degree relative). * **Complications:** Paradoxical embolism (due to pulmonary AVMs) leading to brain abscesses or stroke [1]. * **High-Yield Management:** Iron supplementation for anemia [1]; Bevacizumab for refractory bleeding.
Question 13: A diabetic patient with Enterococcus faecalis sepsis, on intravenous Linezolid, developed high anion gap metabolic acidosis with increased serum lactate and negative ketones. What is the most probable acid-base abnormality?
- A. Type A lactic acidosis due to septic shock
- B. Metabolic acidosis of uncertain etiology
- C. Diabetic ketoacidosis
- D. Type B lactic acidosis due to linezolid (Correct Answer)
Explanation: ### Explanation **Correct Option: D. Type B lactic acidosis due to linezolid** Linezolid is an oxazolidinone antibiotic that inhibits bacterial protein synthesis by binding to the 23S ribosomal RNA of the 50S subunit. However, it can also interfere with **mammalian mitochondrial protein synthesis** due to the structural similarity between bacterial ribosomes and mitochondrial ribosomes. This leads to mitochondrial dysfunction, impairing the aerobic respiratory chain and forcing cells into anaerobic metabolism. The resulting accumulation of lactate occurs **without evidence of tissue hypoxia or hypoperfusion**, which is the hallmark of **Type B Lactic Acidosis** [1]. **Why other options are incorrect:** * **Option A:** Type A lactic acidosis is caused by tissue hypoxia (e.g., septic shock, cardiogenic shock) [1]. While the patient has sepsis, the question does not mention hypotension or signs of poor perfusion; the specific association with Linezolid points toward a drug-induced (Type B) etiology. * **Option B:** The etiology is not "uncertain" because the temporal relationship between Linezolid use and the development of hyperlactatemia is a well-documented clinical phenomenon. * **Option C:** Diabetic ketoacidosis (DKA) is ruled out by the mention of **negative ketones** and the specific finding of increased serum lactate [2]. DKA typically presents with signs like dehydration, air hunger, and the smell of acetone [2]. **Clinical Pearls for NEET-PG:** * **Linezolid Side Effects:** 1. **Hematologic:** Thrombocytopenia (most common with >2 weeks of use). 2. **Neurologic:** Optic and peripheral neuropathy. 3. **Metabolic:** Type B Lactic Acidosis. 4. **Drug Interaction:** Serotonin Syndrome (when used with SSRIs/MAO inhibitors). * **Lactic Acidosis Classification:** * **Type A:** Hypoxic (Shock, severe anemia, CO poisoning) [1]. * **Type B:** Non-hypoxic (Drugs like Metformin, Linezolid, NRTIs; Malignancy; Liver failure) [1].
Question 14: Which of the following is NOT a cause of hyperkalemia?
- A. Digoxin (Correct Answer)
- B. Potassium-sparing diuretic
- C. Renin-angiotensin system blockers
- D. Cyclosporine
Explanation: **Explanation:** The question asks for the drug that is **NOT** a cause of hyperkalemia. However, there is a clinical nuance here: while **Digoxin toxicity** classically causes hyperkalemia, therapeutic doses do not typically result in significant elevation of serum potassium. In the context of standard NEET-PG pharmacology, the other three options are classic, potent causes of drug-induced hyperkalemia. **1. Why Digoxin is the Correct Answer (Contextual):** Digoxin inhibits the **Na+/K+-ATPase pump**. In cases of **acute toxicity**, this inhibition prevents potassium from entering the cells, leading to severe hyperkalemia. However, at therapeutic levels, this effect is minimal. In many MCQ formats, Digoxin is singled out because its relationship with potassium is bidirectional: **hypokalemia** actually predisposes a patient to Digoxin toxicity (by increasing digoxin binding to the ATPase pump). **2. Why the other options are wrong:** * **Potassium-sparing diuretics (e.g., Spironolactone, Amiloride):** These act on the distal nephron to inhibit sodium reabsorption and potassium secretion, directly increasing serum potassium. * **Renin-Angiotensin System (RAS) Blockers (ACE inhibitors/ARBs):** These drugs decrease Aldosterone levels [1]. Since aldosterone is responsible for potassium excretion in the collecting duct, its inhibition leads to potassium retention [1]. * **Cyclosporine:** This calcineurin inhibitor causes hyperkalemia by suppressing aldosterone synthesis and inducing tubular resistance to aldosterone. **High-Yield Clinical Pearls for NEET-PG:** * **Management Tip:** In acute Digoxin poisoning, the degree of **hyperkalemia** is a better predictor of mortality than the digoxin level itself. * **ECG in Hyperkalemia:** Look for tall tented T-waves, PR prolongation, and eventually a "sine wave" pattern. * **Other causes to remember:** Succinylcholine (especially in burn/trauma patients), Beta-blockers, and NSAIDs.
Question 15: A 46-year-old male presented to the emergency with muscle weakness and cramping. He has been taking hydrochlorothiazide for recently diagnosed hypertension. Which of the following is the most likely cause of his symptoms?
- A. Hyponatremia
- B. Hypokalemia (Correct Answer)
- C. Hypoglycemia
- D. Hypocalcemia
Explanation: **Explanation:** The patient is presenting with classic symptoms of **Hypokalemia** (muscle weakness and cramping) secondary to the use of **Hydrochlorothiazide (HCTZ)**, a thiazide diuretic. **Why Hypokalemia is correct:** Thiazide diuretics act on the distal convoluted tubule (DCT) by inhibiting the $Na^+/Cl^-$ symporter. This increases the delivery of sodium to the collecting ducts. In response, the body activates the renin-angiotensin-aldosterone system (RAAS), leading to increased sodium reabsorption in exchange for potassium and hydrogen ions. This results in excessive urinary potassium loss. Low serum potassium levels interfere with the resting membrane potential of muscle cells, leading to **muscle weakness, cramps, and potentially cardiac arrhythmias.** **Why other options are incorrect:** * **Hyponatremia:** While thiazides can cause low sodium, it typically presents with neurological symptoms (confusion, seizures, or lethargy) rather than isolated muscle cramping and weakness. * **Hypoglycemia:** Thiazides actually tend to cause **hyperglycemia** (by inhibiting insulin release and decreasing peripheral glucose utilization), not hypoglycemia. * **Hypocalcemia:** This is a common distractor. Thiazides actually cause **Hypercalcemia** because they increase calcium reabsorption in the DCT. (Note: Loop diuretics like Furosemide cause hypocalcemia). **NEET-PG High-Yield Pearls:** * **Thiazide Side Effects (Mnemonic: GLUC):** Hyper**G**lycemia, Hyper**L**ipidemia, Hyper**U**ricemia (can precipitate Gout), and Hyper**C**alcemia. * **Electrolyte Profile:** Hypokalemic metabolic alkalosis. * **Clinical Tip:** Always monitor serum electrolytes and encourage potassium-rich foods (or consider a potassium-sparing diuretic) when a patient starts HCTZ.
Question 16: Immediately after eating, a man develops swelling of face and lips, respiratory distress, intense pruritus, hypotension, and a feeling of impending doom. What is the most likely diagnosis?
- A. Angioneurotic Edema
- B. Anaphylaxis (Correct Answer)
- C. Myocardial Infarction
- D. Food stuck in throat
Explanation: **Explanation:** The clinical presentation describes a classic case of **Anaphylaxis**, a severe, life-threatening Type I hypersensitivity reaction (IgE-mediated) [2]. The diagnosis is clinical, characterized by the rapid onset (seconds to minutes) of multisystem involvement following exposure to an allergen (in this case, food) [2]. **Why Anaphylaxis is correct:** The patient exhibits signs across multiple organ systems: * **Cutaneous:** Swelling of face/lips (angioedema) and intense pruritus [1]. * **Respiratory:** Distress (likely due to laryngeal edema or bronchospasm) [1]. * **Cardiovascular:** Hypotension and the "feeling of impending doom" (a classic symptom of distributive shock) [1]. The involvement of **two or more systems** (Skin + Respiratory/CV) or **hypotension** after exposure confirms anaphylaxis over simple allergy. **Why other options are incorrect:** * **Angioneurotic Edema:** While present, it is only a component of the reaction. Isolated angioedema does not typically present with hypotension or systemic "impending doom." * **Myocardial Infarction:** While it causes hypotension and distress, it does not explain the acute pruritus, facial swelling, or the immediate temporal link to eating. * **Food stuck in throat:** This causes mechanical airway obstruction (choking) but would not cause hypotension, generalized pruritus, or lip swelling. **NEET-PG High-Yield Pearls:** 1. **Drug of Choice:** Adrenaline (Epinephrine) **1:1000** concentration given **Intramuscularly (IM)** in the anterolateral thigh [1]. 2. **Mechanism:** Adrenaline acts as a physiological antagonist (Alpha-1: vasoconstriction; Beta-1: inotropy; Beta-2: bronchodilation). 3. **Biphasic Reaction:** Symptoms can recur 1–72 hours after initial resolution; hence, patients must be observed [1]. 4. **Lab Marker:** Serum **Tryptase** levels (measured within 1–3 hours) can retrospectively confirm the diagnosis.
Question 17: Which of the following medications can cause erectile dysfunction?
- A. Antihistamines (Correct Answer)
- B. Leukotriene antagonists
- C. Thyroxine
- D. Insulin glargine
Explanation: **Explanation:** **Correct Answer: A. Antihistamines** Erectile dysfunction (ED) is a common side effect of several drug classes, including **Antihistamines** (specifically H1-receptor antagonists like diphenhydramine and promethazine). The underlying mechanism is two-fold: 1. **Anticholinergic Activity:** Many first-generation antihistamines possess significant anticholinergic properties. Penile erection is a parasympathetic-mediated event (via nitric oxide and cGMP); anticholinergics inhibit this parasympathetic outflow, leading to difficulty achieving or maintaining an erection. 2. **Sedative Effects:** Central nervous system depression can decrease libido and arousal. **Analysis of Incorrect Options:** * **B. Leukotriene Antagonists (e.g., Montelukast):** These are primarily associated with neuropsychiatric side effects (mood changes, sleep disturbances) but are not typically linked to erectile dysfunction. * **C. Thyroxine:** Exogenous thyroxine is used to treat hypothyroidism. While *untreated* hypothyroidism or hyperthyroidism can cause sexual dysfunction [1], the replacement therapy itself does not cause ED unless it leads to a state of iatrogenic thyrotoxicosis. * **D. Insulin Glargine:** Insulin is used to manage diabetes mellitus. While diabetes is a leading cause of organic ED due to microvascular and neuropathic damage [1], insulin therapy itself is not the causative agent of ED. **High-Yield Clinical Pearls for NEET-PG:** * **Common Drug Causes of ED:** * **Antihypertensives:** Thiazide diuretics and Beta-blockers (except Nebivolol, which is NO-donating) [2]. * **Antipsychotics:** Due to dopamine antagonism leading to hyperprolactinemia (e.g., Risperidone). * **Antidepressants:** SSRIs (most common cause of delayed ejaculation/decreased libido) [2]. * **Anti-androgens:** Finasteride, Spironolactone, and Ketoconazole [2]. * **Management:** The first-line pharmacological treatment for ED is **PDE-5 Inhibitors** (Sildenafil, Tadalafil), which are contraindicated in patients taking **Nitrates** due to the risk of severe hypotension.
Question 18: HLA-B*1502 is a genetic marker for which of the following conditions?
- A. Systemic lupus erythematosus
- B. Polyarteritis nodosa
- C. Stevens-Johnson syndrome (Correct Answer)
- D. Seronegative spondyloarthritis syndrome
Explanation: **Explanation:** The correct answer is **C. Stevens-Johnson syndrome (SJS)**. **HLA-B*1502** is a genetic allele strongly associated with an increased risk of severe cutaneous adverse reactions (SCARs), specifically **Stevens-Johnson syndrome (SJS)** and **Toxic Epidermal Necrolysis (TEN)**, triggered by the use of **Carbamazepine** [1]. This association is most prevalent in populations of Southeast Asian and Han Chinese descent. The HLA molecule likely presents the drug (or its metabolite) to T-cells, initiating a massive cytotoxic immune response against keratinocytes. Due to this strong correlation, the FDA recommends screening for HLA-B*1502 in high-risk populations before initiating Carbamazepine therapy. **Why other options are incorrect:** * **A. Systemic Lupus Erythemetosus (SLE):** SLE is primarily associated with **HLA-DR2** and **HLA-DR3**. Drug-induced lupus is more commonly linked to "slow acetylator" status (NAT2 polymorphism) rather than HLA-B*1502. * **B. Polyarteritis Nodosa (PAN):** PAN is a systemic necrotizing vasculitis often associated with **Hepatitis B** infection; it does not have a specific association with HLA-B*1502. * **D. Seronegative Spondyloarthritis:** This group of disorders (e.g., Ankylosing Spondylitis) is classically associated with **HLA-B27**. **High-Yield Clinical Pearls for NEET-PG:** * **HLA-B*5701:** Associated with hypersensitivity to **Abacavir** (Antiretroviral). * **HLA-B*5801:** Associated with **Allopurinol**-induced SJS/TEN. * **HLA-DR4:** Associated with Rheumatoid Arthritis and Pemphigus Vulgaris. * **HLA-DQ2/DQ8:** Associated with Celiac Disease.
Question 19: A young female presents with severe abdominal pain, constipation, irrelevant talking, a BP of 160/110 mmHg, heart rate of 120/min, fever, and a positive Watson-Schwartz test in urine. Which of the following drugs should not be used in this condition?
- A. Sodium Valproate
- B. Alcohol
- C. Griseofulvin
- D. All of the above (Correct Answer)
Explanation: ### Explanation **Diagnosis: Acute Intermittent Porphyria (AIP)** The clinical presentation—**abdominal pain, constipation, neuropsychiatric symptoms** (irrelevant talking), and **autonomic instability** (hypertension, tachycardia, fever)—is the classic "tetrad" of AIP [1]. The **Watson-Schwartz test** confirms the diagnosis by detecting elevated levels of porphobilinogen (PBG) in the urine. **The Underlying Concept: Enzyme Induction** AIP is caused by a deficiency in the enzyme *hydroxymethylbilane synthase* [1]. The condition is exacerbated by any factor that induces **Cytochrome P450 (CYP450)** enzymes. When these enzymes are induced, the demand for "Heme" increases, which upregulates **ALA Synthase** (the rate-limiting enzyme). This leads to a toxic accumulation of porphyrin precursors (ALA and PBG), triggering an acute attack. **Why "All of the Above" is Correct:** All three substances listed are potent **porphyrinogenic agents**: * **Sodium Valproate:** An anticonvulsant that induces hepatic enzymes and is strictly contraindicated in porphyria [1]. * **Alcohol:** A common trigger that induces ALA synthase and interferes with the heme biosynthetic pathway [1]. * **Griseofulvin:** An antifungal drug known to be a potent inducer of CYP450 enzymes, frequently cited in exams as a trigger for AIP. **Clinical Pearls for NEET-PG:** * **The 5 P’s of AIP:** **P**ainful abdomen, **P**olyneuropathy, **P**sychiatric disturbances, **P**ink urine (on standing), and **P**recipitated by drugs [1]. * **Safe Drugs:** If a patient with AIP needs treatment, safe options include **Aspirin, Paracetamol, Morphine, and Gabapentin.** * **Management:** The treatment of choice for an acute attack is **Intravenous Hematin** (which provides negative feedback to ALA synthase) and **High-dose Glucose** (which inhibits ALA synthase transcription).
Question 20: Testing of HLA-B57:07 is recommended prior to the initiation of which of the following anti-retroviral agents?
- A. Atazanavir
- B. Nelfinavir
- C. Raltegravir
- D. Abacavir (Correct Answer)
Explanation: **Explanation:** The correct answer is **Abacavir (Option D)**. **1. Why Abacavir is correct:** Abacavir is a Nucleoside Reverse Transcriptase Inhibitor (NRTI) used in HIV treatment. Its use is strongly associated with a potentially life-threatening **Abacavir Hypersensitivity Reaction (HSR)**. This reaction is a Type IV (delayed) hypersensitivity mediated by T-cells. There is a definitive genetic predisposition: patients carrying the **HLA-B*57:01** allele are at a significantly higher risk (approx. 50%) of developing HSR. Therefore, international guidelines (and NEET-PG high-yield facts) mandate screening for this allele before starting Abacavir. If positive, the drug is contraindicated. **2. Why other options are incorrect:** * **Atazanavir (A):** A Protease Inhibitor (PI) known for causing unconjugated hyperbilirubinemia (jaundice) due to UGT1A1 inhibition, but it does not require HLA testing. * **Nelfinavir (B):** An older PI primarily associated with gastrointestinal side effects (diarrhea). No HLA association exists. * **Raltegravir (C):** An Integrase Strand Transfer Inhibitor (INSTI). While it can cause rare skin rashes or SJS, there is no routine genetic screening required for its initiation. **3. High-Yield Clinical Pearls for NEET-PG:** * **Clinical Presentation of HSR:** Fever, rash, GI symptoms (nausea/vomiting), and respiratory symptoms (cough/dyspnea) occurring within the first 6 weeks. * **The "Gold Standard" Rule:** Never "re-challenge" a patient with Abacavir if HSR is suspected; it can lead to fatal anaphylaxis. * **Other HLA-Drug Associations:** * **HLA-B*15:02:** Carbamazepine (SJS/TEN risk in Asians). * **HLA-B*58:01:** Allopurinol (Severe cutaneous adverse reactions). * **HLA-DQB1*06:02:** Clozapine (Agranulocytosis).
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