USMLE Step 1 2026 Pharmacology Practice Exam | Drug
Mechanisms & Side Effects Review | INSTANT PDF
DOWNLOAD
Pharmacology practice exam for USMLE Step 1. This resource contains 200 high-yield questions covering
drug mechanisms, side effects, drug interactions and clinical applications. Each question is styled after Step 1
vignettes. Every answer includes a rationale. Use this exam to master pharmacology for boards.
Key Topics Covered
▪ Autonomic Pharmacology – Cholinergics, anticholinergics, adrenergics, beta-blockers
▪ Cardiovascular & Renal Drugs – Antihypertensives, diuretics, antiarrhythmics, anticoagulants
▪ CNS Pharmacology – Antidepressants, antipsychotics, sedative-hypnotics, anticonvulsants
▪ Antimicrobials – Penicillins, cephalosporins, aminoglycosides, macrolides, tetracyclines,
fluoroquinolones, antivirals
▪ Endocrine & Metabolic Drugs – Insulin, oral hypoglycemics, thyroid drugs, glucocorticoids
▪ Chemotherapy & Immunosuppressants – Antimetabolites, alkylating agents, monoclonal antibodies
▪ Analgesics & Anti-inflammatories – NSAIDs, opioids, local anesthetics
▪ Toxicology & Antidotes
Questions 1–200
1. A 55-year-old male with hypertension is started on a medication that inhibits angiotensin-
converting enzyme. Which adverse effect is most characteristic of this drug class?
A) Dry cough
B) Hyperkalemia
C) Angioedema
D) All of the above
Answer D: All of the above
Rationale: ACE inhibitors cause dry cough (bradykinin accumulation), hyperkalemia (reduced aldosterone),
and angioedema (rare but serious).
2. A 32-year-old woman with myasthenia gravis is prescribed pyridostigmine. Which statement
correctly describes its mechanism of action?
A) Blocks acetylcholine receptors at the neuromuscular junction
,B) Inhibits acetylcholinesterase, increasing acetylcholine at the synapse
C) Promotes acetylcholine release from presynaptic nerve terminals
D) Competitively antagonizes muscarinic receptors
Answer B: Inhibits acetylcholinesterase, increasing acetylcholine at the synapse
Rationale: Pyridostigmine is a reversible acetylcholinesterase inhibitor that prolongs the action of
endogenous acetylcholine at the NMJ.
3. A 68-year-old male with atrial fibrillation is started on warfarin. Which drug interaction would
potentiate the anticoagulant effect of warfarin?
A) Rifampin
B) Vitamin K
C) Amiodarone
D) Oral contraceptives
Answer C: Amiodarone
Rationale: Amiodarone inhibits CYP2C9, reducing warfarin metabolism and increasing INR. Rifampin and
vitamin K decrease warfarin effect.
4. A 45-year-old female with type 2 diabetes is prescribed metformin. Which serious adverse effect
requires immediate discontinuation?
A) Lactic acidosis
B) Weight gain
C) Hypoglycemia
D) Diarrhea
Answer A: Lactic acidosis
Rationale: Metformin can cause lactic acidosis (rare but fatal) in renal impairment or hypoperfusion. GI side
effects are common but not emergent.
5. A 22-year-old male with epilepsy is started on phenytoin. Which adverse effect is associated with
long-term use?
A) Gingival hyperplasia
B) Nystagmus
C) Ataxia
D) Stevens-Johnson syndrome
,Answer A: Gingival hyperplasia
Rationale: Chronic phenytoin use causes gingival overgrowth (good oral hygiene helps). Nystagmus and
ataxia are acute dose-related toxicity.
6. A 60-year-old male with heart failure is prescribed digoxin. Which electrolyte abnormality
increases the risk of digoxin toxicity?
A) Hyperkalemia
B) Hypokalemia
C) Hypercalcemia
D) Hypermagnesemia
Answer B: Hypokalemia
Rationale: Hypokalemia increases digoxin binding to the cardiac Na/K-ATPase, increasing toxicity risk.
Hyperkalemia is protective.
7. A 28-year-old woman with migraine headaches is prescribed sumatriptan. Which receptor does
this drug primarily activate?
A) 5-HT1B/1D
B) 5-HT2A
C) Dopamine D2
D) Norepinephrine alpha-1
Answer A: 5-HT1B/1D
Rationale: Sumatriptan is a 5-HT1B/1D receptor agonist, causing vasoconstriction of cranial vessels and
inhibition of trigeminal nerve activation.
8. A 72-year-old male with Parkinson’s disease is started on carbidopa-levodopa. The addition of
carbidopa serves which purpose?
A) Increases levodopa crossing into the brain
B) Prevents peripheral conversion of levodopa to dopamine
C) Directly stimulates dopamine receptors
D) Reduces dyskinesias
Answer B: Prevents peripheral conversion of levodopa to dopamine
Rationale: Carbidopa inhibits peripheral dopa decarboxylase, reducing nausea and allowing more levodopa
to reach the CNS.
, 9. A 34-year-old male with bipolar disorder is prescribed lithium. Which baseline laboratory tests
are essential before starting therapy?
A) Thyroid function, renal function, pregnancy test
B) Liver function tests
C) Complete blood count
D) Electrocardiogram
Answer A: Thyroid function, renal function, pregnancy test
Rationale: Lithium affects thyroid and kidneys and is teratogenic. Monitor levels regularly (therapeutic 0.6-
1.2 mEq/L).
10. A 55-year-old female with asthma is prescribed albuterol. Which receptor mediates its
bronchodilator effect?
A) Beta-1 adrenergic
B) Beta-2 adrenergic
C) Muscarinic M3
D) Alpha-1 adrenergic
Answer B: Beta-2 adrenergic
Rationale: Albuterol is a selective beta-2 agonist that relaxes bronchial smooth muscle. It has minimal beta-1
cardiac effects.
11. A 62-year-old male with glaucoma is prescribed timolol eye drops. Which systemic adverse effect
should be monitored?
A) Bradycardia and bronchospasm
B) Tachycardia
C) Hypoglycemia
D) Diarrhea
Answer A: Bradycardia and bronchospasm
Rationale: Timolol is a non-selective beta-blocker that can be absorbed systemically, causing bradycardia
and exacerbating asthma/COPD.
Mechanisms & Side Effects Review | INSTANT PDF
DOWNLOAD
Pharmacology practice exam for USMLE Step 1. This resource contains 200 high-yield questions covering
drug mechanisms, side effects, drug interactions and clinical applications. Each question is styled after Step 1
vignettes. Every answer includes a rationale. Use this exam to master pharmacology for boards.
Key Topics Covered
▪ Autonomic Pharmacology – Cholinergics, anticholinergics, adrenergics, beta-blockers
▪ Cardiovascular & Renal Drugs – Antihypertensives, diuretics, antiarrhythmics, anticoagulants
▪ CNS Pharmacology – Antidepressants, antipsychotics, sedative-hypnotics, anticonvulsants
▪ Antimicrobials – Penicillins, cephalosporins, aminoglycosides, macrolides, tetracyclines,
fluoroquinolones, antivirals
▪ Endocrine & Metabolic Drugs – Insulin, oral hypoglycemics, thyroid drugs, glucocorticoids
▪ Chemotherapy & Immunosuppressants – Antimetabolites, alkylating agents, monoclonal antibodies
▪ Analgesics & Anti-inflammatories – NSAIDs, opioids, local anesthetics
▪ Toxicology & Antidotes
Questions 1–200
1. A 55-year-old male with hypertension is started on a medication that inhibits angiotensin-
converting enzyme. Which adverse effect is most characteristic of this drug class?
A) Dry cough
B) Hyperkalemia
C) Angioedema
D) All of the above
Answer D: All of the above
Rationale: ACE inhibitors cause dry cough (bradykinin accumulation), hyperkalemia (reduced aldosterone),
and angioedema (rare but serious).
2. A 32-year-old woman with myasthenia gravis is prescribed pyridostigmine. Which statement
correctly describes its mechanism of action?
A) Blocks acetylcholine receptors at the neuromuscular junction
,B) Inhibits acetylcholinesterase, increasing acetylcholine at the synapse
C) Promotes acetylcholine release from presynaptic nerve terminals
D) Competitively antagonizes muscarinic receptors
Answer B: Inhibits acetylcholinesterase, increasing acetylcholine at the synapse
Rationale: Pyridostigmine is a reversible acetylcholinesterase inhibitor that prolongs the action of
endogenous acetylcholine at the NMJ.
3. A 68-year-old male with atrial fibrillation is started on warfarin. Which drug interaction would
potentiate the anticoagulant effect of warfarin?
A) Rifampin
B) Vitamin K
C) Amiodarone
D) Oral contraceptives
Answer C: Amiodarone
Rationale: Amiodarone inhibits CYP2C9, reducing warfarin metabolism and increasing INR. Rifampin and
vitamin K decrease warfarin effect.
4. A 45-year-old female with type 2 diabetes is prescribed metformin. Which serious adverse effect
requires immediate discontinuation?
A) Lactic acidosis
B) Weight gain
C) Hypoglycemia
D) Diarrhea
Answer A: Lactic acidosis
Rationale: Metformin can cause lactic acidosis (rare but fatal) in renal impairment or hypoperfusion. GI side
effects are common but not emergent.
5. A 22-year-old male with epilepsy is started on phenytoin. Which adverse effect is associated with
long-term use?
A) Gingival hyperplasia
B) Nystagmus
C) Ataxia
D) Stevens-Johnson syndrome
,Answer A: Gingival hyperplasia
Rationale: Chronic phenytoin use causes gingival overgrowth (good oral hygiene helps). Nystagmus and
ataxia are acute dose-related toxicity.
6. A 60-year-old male with heart failure is prescribed digoxin. Which electrolyte abnormality
increases the risk of digoxin toxicity?
A) Hyperkalemia
B) Hypokalemia
C) Hypercalcemia
D) Hypermagnesemia
Answer B: Hypokalemia
Rationale: Hypokalemia increases digoxin binding to the cardiac Na/K-ATPase, increasing toxicity risk.
Hyperkalemia is protective.
7. A 28-year-old woman with migraine headaches is prescribed sumatriptan. Which receptor does
this drug primarily activate?
A) 5-HT1B/1D
B) 5-HT2A
C) Dopamine D2
D) Norepinephrine alpha-1
Answer A: 5-HT1B/1D
Rationale: Sumatriptan is a 5-HT1B/1D receptor agonist, causing vasoconstriction of cranial vessels and
inhibition of trigeminal nerve activation.
8. A 72-year-old male with Parkinson’s disease is started on carbidopa-levodopa. The addition of
carbidopa serves which purpose?
A) Increases levodopa crossing into the brain
B) Prevents peripheral conversion of levodopa to dopamine
C) Directly stimulates dopamine receptors
D) Reduces dyskinesias
Answer B: Prevents peripheral conversion of levodopa to dopamine
Rationale: Carbidopa inhibits peripheral dopa decarboxylase, reducing nausea and allowing more levodopa
to reach the CNS.
, 9. A 34-year-old male with bipolar disorder is prescribed lithium. Which baseline laboratory tests
are essential before starting therapy?
A) Thyroid function, renal function, pregnancy test
B) Liver function tests
C) Complete blood count
D) Electrocardiogram
Answer A: Thyroid function, renal function, pregnancy test
Rationale: Lithium affects thyroid and kidneys and is teratogenic. Monitor levels regularly (therapeutic 0.6-
1.2 mEq/L).
10. A 55-year-old female with asthma is prescribed albuterol. Which receptor mediates its
bronchodilator effect?
A) Beta-1 adrenergic
B) Beta-2 adrenergic
C) Muscarinic M3
D) Alpha-1 adrenergic
Answer B: Beta-2 adrenergic
Rationale: Albuterol is a selective beta-2 agonist that relaxes bronchial smooth muscle. It has minimal beta-1
cardiac effects.
11. A 62-year-old male with glaucoma is prescribed timolol eye drops. Which systemic adverse effect
should be monitored?
A) Bradycardia and bronchospasm
B) Tachycardia
C) Hypoglycemia
D) Diarrhea
Answer A: Bradycardia and bronchospasm
Rationale: Timolol is a non-selective beta-blocker that can be absorbed systemically, causing bradycardia
and exacerbating asthma/COPD.
