USMLE Step 1 Pharmacology Mastery: 100+ High-Yield
Questions Aligned with First Aid 2025
Focus: Comprehensive practice with tightly focused First Aid
alignment
Use: Ideal for timed self-testing and exam simulation
Q1
A 52-year-old non-binary patient with hypertension and
chronic heart failure starts a new medication and develops an
uncontrollable dry cough two months later.
Lab: Normal renal function.
Which drug is most likely responsible?
A. Amlodipine
B. Lisinopril ✅
C. Metoprolol
D. Hydrochlorothiazide
✅ Correct: Lisinopril elevates bradykinin levels → persistent
cough.
❌ Incorrect:
Amlodipine → peripheral edema, not cough.
Metoprolol → bronchospasm risk in asthma, not cough.
, HCTZ → electrolyte abnormalities, not cough.
FA 2025: p. 260 “ACE inhibitors – adverse effects.”
Tip: New dry cough in HF/HTN management often points
to ACE inhibitor.
Q2
A 28-year-old named Alex on haloperidol for schizophrenia
presents with the head pulled upward and mouth twisted,
starting last night.
Which is the most appropriate initial therapy?
A. Discontinue haloperidol
B. Administer oral benztropine ✅
C. Switch to clozapine
D. Add sertraline
✅ Correct: Benztropine treats acute dystonic reactions due to
dopamine-chol balance.
❌ Incorrect:
Discontinuation → no immediate relief.
Clozapine → not first-line for acute dystonia.
Sertraline → irrelevant.
FA 2025: p. 314 “Acute EPS – dystonia.”
Tip: EPS within days — think dystonia; treat with
anticholinergic.
,Q3
A 63-year-old on allopurinol for gout and azathioprine for
rheumatoid arthritis reports fever, sore throat, and bruising.
Which mechanism explains this interaction?
A. CYP450 inhibition
B. Xanthine oxidase inhibition leading to azathioprine toxicity
✅
C. P-gp induction
D. Enhanced renal clearance
✅ Correct: Inhibiting xanthine oxidase decreases azathioprine
breakdown → marrow suppression.
❌ Incorrect: Others unrelated.
FA 2025: p. 356 “Allopurinol-azathioprine interaction.”
Tip: Always reduce azathioprine dose (25%) and monitor CBC
when paired with allopurinol.
Q4
A 46-year-old on warfarin for atrial fibrillation starts drinking
grapefruit juice daily and returns with INR of 6.2.
Which mechanism explains the elevated INR?
A. CYP2C9 induction
B. CYP3A4 inhibition ✅
C. Increased vitamin K intake
D. P-gp induction
, ✅ Correct: Grapefruit juice inhibits CYP3A4 → reduced
warfarin metabolism.
❌ Incorrect:
Induction → opposite effect.
Vitamin K → lowers INR.
P-gp → no effect.
FA 2025: p. 288 “Warfarin — drug interactions.”
Tip: Always ask about grapefruit juice when managing
warfarin.
Q5
35-year-old on isoniazid for latent TB presents with peripheral
neuropathy and elevated LFTs.
What should be added to reduce this risk?
A. Thiamine
B. Vitamin D
C. Pyridoxine ✅
D. Folic acid
✅ Correct: Pyridoxine prevents INH-induced neuropathy and
hepatic effects.
❌ Incorrect: Others irrelevant.
FA 2025: p. 248 “INH – adverse effects & prevention.”
Tip: Always supplement pyridoxine with INH therapy.
Q6
Questions Aligned with First Aid 2025
Focus: Comprehensive practice with tightly focused First Aid
alignment
Use: Ideal for timed self-testing and exam simulation
Q1
A 52-year-old non-binary patient with hypertension and
chronic heart failure starts a new medication and develops an
uncontrollable dry cough two months later.
Lab: Normal renal function.
Which drug is most likely responsible?
A. Amlodipine
B. Lisinopril ✅
C. Metoprolol
D. Hydrochlorothiazide
✅ Correct: Lisinopril elevates bradykinin levels → persistent
cough.
❌ Incorrect:
Amlodipine → peripheral edema, not cough.
Metoprolol → bronchospasm risk in asthma, not cough.
, HCTZ → electrolyte abnormalities, not cough.
FA 2025: p. 260 “ACE inhibitors – adverse effects.”
Tip: New dry cough in HF/HTN management often points
to ACE inhibitor.
Q2
A 28-year-old named Alex on haloperidol for schizophrenia
presents with the head pulled upward and mouth twisted,
starting last night.
Which is the most appropriate initial therapy?
A. Discontinue haloperidol
B. Administer oral benztropine ✅
C. Switch to clozapine
D. Add sertraline
✅ Correct: Benztropine treats acute dystonic reactions due to
dopamine-chol balance.
❌ Incorrect:
Discontinuation → no immediate relief.
Clozapine → not first-line for acute dystonia.
Sertraline → irrelevant.
FA 2025: p. 314 “Acute EPS – dystonia.”
Tip: EPS within days — think dystonia; treat with
anticholinergic.
,Q3
A 63-year-old on allopurinol for gout and azathioprine for
rheumatoid arthritis reports fever, sore throat, and bruising.
Which mechanism explains this interaction?
A. CYP450 inhibition
B. Xanthine oxidase inhibition leading to azathioprine toxicity
✅
C. P-gp induction
D. Enhanced renal clearance
✅ Correct: Inhibiting xanthine oxidase decreases azathioprine
breakdown → marrow suppression.
❌ Incorrect: Others unrelated.
FA 2025: p. 356 “Allopurinol-azathioprine interaction.”
Tip: Always reduce azathioprine dose (25%) and monitor CBC
when paired with allopurinol.
Q4
A 46-year-old on warfarin for atrial fibrillation starts drinking
grapefruit juice daily and returns with INR of 6.2.
Which mechanism explains the elevated INR?
A. CYP2C9 induction
B. CYP3A4 inhibition ✅
C. Increased vitamin K intake
D. P-gp induction
, ✅ Correct: Grapefruit juice inhibits CYP3A4 → reduced
warfarin metabolism.
❌ Incorrect:
Induction → opposite effect.
Vitamin K → lowers INR.
P-gp → no effect.
FA 2025: p. 288 “Warfarin — drug interactions.”
Tip: Always ask about grapefruit juice when managing
warfarin.
Q5
35-year-old on isoniazid for latent TB presents with peripheral
neuropathy and elevated LFTs.
What should be added to reduce this risk?
A. Thiamine
B. Vitamin D
C. Pyridoxine ✅
D. Folic acid
✅ Correct: Pyridoxine prevents INH-induced neuropathy and
hepatic effects.
❌ Incorrect: Others irrelevant.
FA 2025: p. 248 “INH – adverse effects & prevention.”
Tip: Always supplement pyridoxine with INH therapy.
Q6
