USMLE Pharmacology

Question 1

A patient on warfarin develops supratherapeutic INR after starting a new antibiotic. Which mechanism best explains this interaction?

Accepted Answer

Inhibition of CYP2C9 by the antibiotic

Answer

Induction of CYP3A4

Answer

Displacement from plasma proteins

Answer

Direct inhibition of clotting factors

Question 2

Which beta-blocker is cardioselective and preferred in a patient with COPD requiring beta-blockade?

Accepted Answer

Metoprolol

Answer

Propranolol

Answer

Carvedilol

Answer

Labetalol

Question 3

A patient with type 2 diabetes develops lactic acidosis. Which medication is most likely responsible?

Accepted Answer

Metformin

Answer

Glipizide

Answer

Sitagliptin

Answer

Pioglitazone

Question 4

Which antiepileptic drug works by blocking voltage-gated sodium channels and is also used for neuropathic pain and bipolar disorder?

Accepted Answer

Carbamazepine

Answer

Valproate

Answer

Ethosuximide

Answer

Phenobarbital

Question 5

A patient develops gynecomastia while taking spironolactone. What is the mechanism of this side effect?

Accepted Answer

Antagonism of androgen receptors

Answer

Inhibition of 5-alpha reductase

Answer

Inhibition of CYP17A1

Answer

Stimulation of estrogen receptors

Question 6

Which ACE inhibitor side effect is class-specific and due to bradykinin accumulation?

Accepted Answer

Dry cough

Answer

Hyperkalemia

Answer

First-dose hypotension

Answer

Angioedema