USMLE Pharmacology 2 — Questions and Answers
Question 1: A patient taking isoniazid for TB develops peripheral neuropathy. Which vitamin supplementation prevents this?
- Pyridoxine (B6) (Correct answer)
- Thiamine (B1)
- Cyanocobalamin (B12)
- Niacin (B3)
Correct answer: Pyridoxine (B6)
Isoniazid competitively inhibits pyridoxal phosphate (active B6), causing peripheral neuropathy; B6 supplementation is given prophylactically.
Question 2: Which mechanism explains why aminoglycosides are bactericidal despite being protein synthesis inhibitors?
- They cause misreading of mRNA, producing abnormal proteins that disrupt cell membranes (Correct answer)
- They bind the 50S subunit and block translocation
- They inhibit peptidyl transferase activity
- They prevent binding of aminoacyl-tRNA
Correct answer: They cause misreading of mRNA, producing abnormal proteins that disrupt cell membranes
Aminoglycosides cause misreading at the 30S ribosome, incorporating wrong amino acids that create aberrant proteins which disrupt the cell membrane, causing bactericidal cell death.
Question 3: A patient with HIV on antiretroviral therapy develops central adiposity, peripheral fat wasting, and hyperlipidemia. Which drug class causes this metabolic syndrome?
- Protease inhibitors (Correct answer)
- NNRTIs
- NRTIs
- Integrase inhibitors
Correct answer: Protease inhibitors
Protease inhibitors cause lipodystrophy syndrome characterized by central fat accumulation, peripheral lipoatrophy, and dyslipidemia.
Question 4: Which anticoagulant requires no laboratory monitoring and directly inhibits thrombin (Factor IIa)?
- Dabigatran (Correct answer)
- Rivaroxaban
- Apixaban
- Fondaparinux
Correct answer: Dabigatran
Dabigatran is a direct thrombin inhibitor that requires no routine INR monitoring and is reversed by idarucizumab.
Question 5: A patient develops 'red man syndrome' during IV vancomycin infusion. What is the underlying mechanism?
- Direct mast cell degranulation (non-IgE mediated) (Correct answer)
- IgE-mediated type I hypersensitivity
- Complement activation
- Immune complex deposition
Correct answer: Direct mast cell degranulation (non-IgE mediated)
Vancomycin causes non-immunologic direct mast cell degranulation, releasing histamine and causing flushing/erythema; slowing the infusion rate prevents this reaction.
Question 6: Which diuretic acts on the thick ascending limb of the loop of Henle and inhibits the Na-K-2Cl cotransporter?
- Furosemide (Correct answer)
- Hydrochlorothiazide
- Spironolactone
- Acetazolamide
Correct answer: Furosemide
Furosemide inhibits the Na-K-2Cl cotransporter in the thick ascending limb of the loop of Henle, producing powerful natriuresis and diuresis.
USMLE Pharmacology 2
A patient taking isoniazid for TB develops peripheral neuropathy.
Which vitamin supplementation prevents this?