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NBME-style Pharmacology practice exam 2025 Questions and
Correct Answers (Verified Answers) Plus Rationales 2025
. The questions are designed to reflect the style and clinical focus seen on NBME Step 1 and Step 2 exams. 1. A 25-year-old man presents with muscle fasciculations and paralysis after being exposed to an organophosphate pesticide. Which of the following drugs is most appropriate for reversing the peripheral effects? A. Physostigmine B. Pralidoxime C. Neostigmine D. Edrophonium
Pralidoxime reactivates acetylcholinesterase inhibited by
organophosphates, reversing peripheral effects like paralysis. Central
effects require atropine.
- A patient with asthma is given a β2-agonist. What is the most likely mechanism of this medication?
A. Inhibition of phospholipase A B. Antagonism of leukotriene receptors C. Stimulation of adenylate cyclase leading to increased cAMP D. Blockade of muscarinic receptors
β2-agonists stimulate adenylate cyclase via Gs proteins, increasing
cAMP in bronchial smooth muscle and causing bronchodilation.
- A patient is started on a new anti-hypertensive that causes a dry cough. Which drug is most likely responsible? A. Losartan B. Amlodipine C. Lisinopril D. Hydrochlorothiazide
ACE inhibitors like lisinopril increase bradykinin levels, leading to the
characteristic dry cough.
- Which drug is a competitive antagonist of aldosterone? A. Spironolactone B. Furosemide C. Acetazolamide D. Amiloride
C. Phenelzine D. Bupropion
Fluoxetine is a prototypical SSRI, used in depression and anxiety
disorders.
- A 60-year-old man with Parkinson disease is given carbidopa with levodopa. What is the role of carbidopa? A. Enhances conversion of levodopa to dopamine B. Inhibits peripheral decarboxylation of levodopa C. Prevents dopamine degradation in CNS D. Crosses the BBB to activate dopamine receptors
Carbidopa inhibits dopa decarboxylase in the periphery, reducing side
effects and increasing levodopa availability to the CNS.
- Which of the following is used as a treatment for opioid overdose? A. Methadone B. Naloxone C. Buprenorphine D. Morphine
Naloxone is a competitive opioid receptor antagonist used to reverse
opioid toxicity.
10.A diabetic patient is given a drug that causes lactic acidosis in rare cases. What is this drug? A. Glipizide B. Metformin C. Pioglitazone D. Acarbose
Metformin can cause lactic acidosis, especially in renal impairment.
11.What is the mechanism of action of digoxin? A. Beta-1 adrenergic receptor agonist B. Inhibits Na+/K+ ATPase, increasing intracellular Ca²⁺ C. Calcium channel blockade D. Enhances phosphodiesterase activity
Digoxin inhibits Na+/K+ ATPase, indirectly increasing intracellular
calcium in cardiac myocytes.
12.Which of the following antibiotics can cause tendon rupture? A. Azithromycin B. Amoxicillin C. Ciprofloxacin D. Vancomycin
A. Tetracycline B. Azithromycin C. Gentamicin D. Doxycycline
Macrolides like azithromycin inhibit bacterial protein synthesis at the
50S subunit.
16.Which antipsychotic is associated with agranulocytosis? A. Risperidone B. Olanzapine C. Clozapine D. Haloperidol
Clozapine requires weekly WBC monitoring due to the risk of
agranulocytosis.
17.Which drug is used to treat methotrexate toxicity? A. N-acetylcysteine B. Pyridoxine C. Leucovorin D. Vitamin K
Leucovorin is folinic acid and rescues normal cells from methotrexate
toxicity.
18.A child is treated for acute lymphoblastic leukemia and develops hyperuricemia. Which drug prevents this? A. Cyclophosphamide B. Cisplatin C. Allopurinol D. Bleomycin
Allopurinol prevents uric acid accumulation by inhibiting xanthine
oxidase.
19.Which of the following causes gingival hyperplasia? A. Propranolol B. Phenytoin C. Levetiracetam D. Carbamazepine
Phenytoin is a classic antiepileptic associated with gingival overgrowth.
20.What is the antidote for acetaminophen overdose? A. N-acetylcysteine B. Flumazenil C. Deferoxamine D. Atropine
23.Which medication is contraindicated in pregnancy due to risk of fetal renal toxicity? A. Erythromycin B. Amoxicillin C. ACE inhibitors D. Heparin
ACE inhibitors can cause fetal renal damage and are contraindicated in
pregnancy.
24.What is the mechanism of action of sulfonylureas? A. Enhance insulin sensitivity B. Inhibit glucose absorption C. Close K⁺ channels in β-cells to stimulate insulin release D. Activate insulin receptors
Sulfonylureas increase insulin secretion by inhibiting ATP-sensitive K⁺
channels.
25.Which of the following drugs causes ototoxicity? A. Amoxicillin B. Furosemide
C. Spironolactone D. Hydrochlorothiazide
Loop diuretics like furosemide can cause dose-related hearing loss.
26.A patient with gout is treated with colchicine. What is its mechanism? A. Inhibits microtubule polymerization B. Inhibits xanthine oxidase C. Inhibits urate reabsorption D. Promotes urate excretion
Colchicine disrupts microtubule formation, impairing neutrophil function
during gout attacks.
27.Which drug class is most likely to cause torsades de pointes? A. ACE inhibitors B. Beta-blockers C. Class III antiarrhythmics D. Calcium channel blockers
Class III antiarrhythmics like sotalol prolong QT interval and increase
torsades risk.
28.Which of the following drugs inhibits bacterial DNA gyrase?
Dantrolene is used to treat neuroleptic malignant syndrome by reducing
muscle contraction.
31.Which drug is used in the treatment of alcohol withdrawal? A. Haloperidol B. Diazepam C. Propranolol D. Clonidine
Long-acting benzodiazepines like diazepam prevent seizures in alcohol
withdrawal.
32.What is the primary toxicity of doxorubicin? A. Pulmonary fibrosis B. Cardiomyopathy C. Nephrotoxicity D. Ototoxicity
Doxorubicin causes dose-dependent cardiotoxicity due to free radical
generation.
33.Which antibiotic is associated with pseudomembranous colitis? A. Clindamycin B. Cefazolin
C. Amoxicillin D. Azithromycin
Clindamycin disrupts gut flora, promoting Clostridium difficile
overgrowth.
34.What is the mechanism of action of sildenafil? A. α1 antagonist B. Inhibits phosphodiesterase- 5 C. Increases testosterone D. Muscarinic agonist
Sildenafil inhibits PDE5, increasing cGMP and promoting smooth muscle
relaxation in the corpus cavernosum.
35.Which drug is a first-line treatment for status epilepticus? A. Phenytoin B. Lorazepam C. Levetiracetam D. Valproic acid
Benzodiazepines like lorazepam are first-line due to rapid action on
GABA-A receptors.
Lithium interferes with thyroid hormone synthesis, leading to
hypothyroidism.
39.Which agent binds to ergosterol and forms pores in fungal membranes? A. Fluconazole B. Amphotericin B C. Griseofulvin D. Terbinafine
Amphotericin B binds ergosterol and disrupts fungal cell membranes.
40.A patient with atrial fibrillation is given warfarin. What lab value should be monitored? A. aPTT B. INR C. Bleeding time D. Platelet count
INR (a standardized PT) is used to monitor warfarin therapy.
41.Which drug causes hemolysis in G6PD-deficient patients? A. Erythromycin B. Ciprofloxacin
C. Sulfamethoxazole D. Rifampin
Sulfamethoxazole is an oxidizing agent that can trigger hemolysis in
G6PD deficiency.
42.What is the mechanism of action of atropine? A. Muscarinic receptor antagonist B. α-adrenergic antagonist C. β-adrenergic agonist D. Cholinesterase inhibitor
Atropine blocks muscarinic receptors, reducing parasympathetic effects.
43.Which antipsychotic has the highest risk of extrapyramidal symptoms? A. Quetiapine B. Haloperidol C. Clozapine D. Aripiprazole
Haloperidol is a high-potency typical antipsychotic strongly associated
with EPS.
44.Which antibiotic is contraindicated in children due to teeth discoloration?
47.Which diuretic is used to treat altitude sickness? A. Furosemide B. Acetazolamide C. Spironolactone D. Hydrochlorothiazide
Acetazolamide causes metabolic acidosis, which stimulates ventilation,
useful at high altitude.
48.What is a common side effect of niacin? A. Constipation B. Flushing C. Visual disturbances D. Hair loss
Niacin causes prostaglandin-mediated flushing, which can be reduced
with aspirin.
49.Which of the following increases insulin sensitivity? A. Glipizide B. Pioglitazone C. Sitagliptin D. Acarbose
Pioglitazone is a PPARγ agonist that improves insulin sensitivity.
50.A patient takes levothyroxine. What is its mechanism? A. Thyroid hormone receptor agonist B. TSH receptor agonist C. Inhibits thyroid peroxidase D. Suppresses TSH release
Levothyroxine is synthetic T4 and acts as a thyroid hormone receptor
agonist.
51.Which drug can cause gynecomastia as a side effect? A. Enalapril B. Spironolactone C. Furosemide D. Hydrochlorothiazide
Spironolactone has antiandrogenic effects that can lead to
gynecomastia.
52.Which drug is used to treat serotonin syndrome? A. Fluoxetine B. Cyproheptadine
