USMLE Pharmacology 2

Question 1

A patient taking isoniazid for TB develops peripheral neuropathy. Which vitamin supplementation prevents this?

Accepted Answer

Pyridoxine (B6)

Answer

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?

Accepted Answer

They cause misreading of mRNA, producing abnormal proteins that disrupt cell membranes

Answer

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?

Accepted Answer

Protease inhibitors

Answer

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)?

Accepted Answer

Dabigatran

Answer

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?

Accepted Answer

Direct mast cell degranulation (non-IgE mediated)

Answer

Vancomycin causes non-immunologic direct mast cell degranulation, releasing histamine and causing flushing/erythema; slowing the infusion rate prevents this reaction.

USMLE Practice Test

USMLE Practice Test

USMLE Pharmacology 2