USMLE STEP 1 PHARMACOLOGY | PRACTICE QUESTIONS WITH VERIFIED ANSWERS AND RATIONALES
USMLE Step 1 – Pharmacology Practice Questions
1. Which class of drugs works by inhibiting the enzyme HMG-CoA reductase?
1. Beta-blockers
2. Statins
3. ACE inhibitors
4. Loop diuretics
Answer: 2. Statins
Rationale: Statins inhibit HMG-CoA reductase, the rate-limiting enzyme in cholesterol biosynthesis, thereby
lowering LDL cholesterol levels.
2. A patient taking warfarin develops an elevated INR after starting a new antibiotic. Which mechanism most likely
explains this interaction?
1. The antibiotic increases warfarin metabolism via CYP450 induction
2. The antibiotic inhibits CYP450 enzymes, decreasing warfarin metabolism and increasing its anticoagulant
effect
3. The antibiotic has no effect on warfarin metabolism
4. The antibiotic increases vitamin K synthesis
Answer: 2. The antibiotic inhibits CYP450 enzymes, decreasing warfarin metabolism and increasing its
anticoagulant effect
Rationale: Many antibiotics inhibit cytochrome P450 enzymes responsible for warfarin metabolism, leading to
increased warfarin plasma levels, a higher INR, and increased bleeding risk.
3. What is the mechanism of action of beta-blockers in treating hypertension?
1. Blocking calcium channels in vascular smooth muscle
2. Blocking beta-adrenergic receptors, reducing heart rate and cardiac output
3. Inhibiting angiotensin-converting enzyme
4. Blocking sodium channels in cardiac tissue
Answer: 2. Blocking beta-adrenergic receptors, reducing heart rate and cardiac output
Rationale: Beta-blockers competitively block beta-adrenergic receptors, reducing heart rate, myocardial
contractility, and cardiac output, thereby lowering blood pressure.
4. Which drug class is associated with a dry, persistent cough as a common side effect due to bradykinin
accumulation?
1. Angiotensin receptor blockers (ARBs)
2. ACE inhibitors
3. Calcium channel blockers
4. Thiazide diuretics
Answer: 2. ACE inhibitors
Rationale: ACE inhibitors prevent the breakdown of bradykinin (in addition to blocking angiotensin II
formation), and bradykinin accumulation in the lungs is thought to cause the characteristic dry cough seen with
this drug class.
5. What is the primary mechanism of action of penicillin antibiotics?
1. Inhibiting bacterial protein synthesis at the 30S ribosomal subunit
2. Inhibiting bacterial cell wall synthesis by binding penicillin-binding proteins
3. Inhibiting bacterial DNA gyrase
4. Inhibiting folic acid synthesis
Answer: 2. Inhibiting bacterial cell wall synthesis by binding penicillin-binding proteins
USMLE Step 1 – Pharmacology Practice Questions
1. Which class of drugs works by inhibiting the enzyme HMG-CoA reductase?
1. Beta-blockers
2. Statins
3. ACE inhibitors
4. Loop diuretics
Answer: 2. Statins
Rationale: Statins inhibit HMG-CoA reductase, the rate-limiting enzyme in cholesterol biosynthesis, thereby
lowering LDL cholesterol levels.
2. A patient taking warfarin develops an elevated INR after starting a new antibiotic. Which mechanism most likely
explains this interaction?
1. The antibiotic increases warfarin metabolism via CYP450 induction
2. The antibiotic inhibits CYP450 enzymes, decreasing warfarin metabolism and increasing its anticoagulant
effect
3. The antibiotic has no effect on warfarin metabolism
4. The antibiotic increases vitamin K synthesis
Answer: 2. The antibiotic inhibits CYP450 enzymes, decreasing warfarin metabolism and increasing its
anticoagulant effect
Rationale: Many antibiotics inhibit cytochrome P450 enzymes responsible for warfarin metabolism, leading to
increased warfarin plasma levels, a higher INR, and increased bleeding risk.
3. What is the mechanism of action of beta-blockers in treating hypertension?
1. Blocking calcium channels in vascular smooth muscle
2. Blocking beta-adrenergic receptors, reducing heart rate and cardiac output
3. Inhibiting angiotensin-converting enzyme
4. Blocking sodium channels in cardiac tissue
Answer: 2. Blocking beta-adrenergic receptors, reducing heart rate and cardiac output
Rationale: Beta-blockers competitively block beta-adrenergic receptors, reducing heart rate, myocardial
contractility, and cardiac output, thereby lowering blood pressure.
4. Which drug class is associated with a dry, persistent cough as a common side effect due to bradykinin
accumulation?
1. Angiotensin receptor blockers (ARBs)
2. ACE inhibitors
3. Calcium channel blockers
4. Thiazide diuretics
Answer: 2. ACE inhibitors
Rationale: ACE inhibitors prevent the breakdown of bradykinin (in addition to blocking angiotensin II
formation), and bradykinin accumulation in the lungs is thought to cause the characteristic dry cough seen with
this drug class.
5. What is the primary mechanism of action of penicillin antibiotics?
1. Inhibiting bacterial protein synthesis at the 30S ribosomal subunit
2. Inhibiting bacterial cell wall synthesis by binding penicillin-binding proteins
3. Inhibiting bacterial DNA gyrase
4. Inhibiting folic acid synthesis
Answer: 2. Inhibiting bacterial cell wall synthesis by binding penicillin-binding proteins
