These 15 board-style pharmacology questions cover the drug facts that come up again and again on medical school exams and the USMLE: receptors, classic side effects, toxicities and key mechanisms. Pick an answer, then open Answer and Explanation to check yourself.
Questions written by Dr. Ray Makar, retired dermatologist and USMLE teacher.
Autonomic and Cardiovascular Drugs
Q1. A 45-year-old man with hypertension and benign prostatic hyperplasia (BPH) starts a new medication that improves his urinary symptoms but makes him dizzy when he stands up. Which drug is most likely responsible?
A. Atenolol
B. Furosemide
C. Prazosin
D. Enalapril
Answer and Explanation
C. Prazosin. Prazosin is an α1-blocker. It relaxes smooth muscle in the prostate and bladder neck (better urine flow) and in blood vessels (lower blood pressure). Its classic side effect is orthostatic hypotension, especially after the first dose.
Q2. A patient with asthma is given a new drug that improves her breathing but causes tremor and palpitations. Which receptor is this drug most likely acting on?
A. α1-adrenergic receptor
B. β1-adrenergic receptor
C. β2-adrenergic receptor
D. Muscarinic receptor
Answer and Explanation
C. β2-adrenergic receptor. β2-agonists such as albuterol relax bronchial smooth muscle. Tremor comes from β2 stimulation of skeletal muscle, and palpitations from some β1 stimulation at higher doses.
Q3. Which of the following is a β1-selective blocker useful for treating hypertension in a patient with asthma?
A. Carvedilol
B. Labetalol
C. Metoprolol
D. Propranolol
Answer and Explanation
C. Metoprolol. Metoprolol (like atenolol) is cardioselective, so it is less likely to cause bronchospasm. Propranolol, carvedilol and labetalol also block β2 receptors and can worsen asthma.
Q4. A 70-year-old patient with atrial fibrillation takes digoxin. Which findings suggest digoxin toxicity?
A. Bradycardia and yellow vision
B. Diarrhea and flushing
C. Muscle twitching and dry mouth
D. Tremor and hyperthermia
Answer and Explanation
A. Bradycardia and yellow vision. Digoxin toxicity causes nausea and vomiting, blurred or yellow vision (xanthopsia), bradycardia and arrhythmias, and hyperkalemia. Hypokalemia makes toxicity more likely. The antidote is digoxin-specific antibody fragments (Digibind).
Q5. Which side effect is most likely associated with spironolactone?
A. Hypercalcemia
B. Hyperglycemia
C. Hyperkalemia
D. Metabolic alkalosis
Answer and Explanation
C. Hyperkalemia. Spironolactone is a potassium-sparing diuretic that blocks aldosterone receptors in the collecting duct. Potassium must be monitored, especially in patients with kidney disease or those also taking ACE inhibitors or ARBs.
Q6. A man taking spironolactone for heart failure develops breast enlargement. This effect is caused by which property of the drug?
A. Antiandrogen effect
B. Aldosterone receptor stimulation
C. Carbonic anhydrase inhibition
D. Loop of Henle blockade
Answer and Explanation
A. Antiandrogen effect. Spironolactone also blocks androgen receptors, which can cause gynecomastia and decreased libido in men. Eplerenone is more selective for the aldosterone receptor and causes far less gynecomastia.
Q7. A 30-year-old man develops facial flushing after starting niacin for hyperlipidemia. What causes this side effect?
A. Acetylcholine release
B. Catecholamine excess
C. Histamine release
D. Prostaglandin-mediated vasodilation
Answer and Explanation
D. Prostaglandin-mediated vasodilation. Niacin flushing is caused by prostaglandins. Taking aspirin about 30 minutes before the dose reduces it.
Antibiotics and Chemotherapy
Q8. Which of the following antibiotics inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit?
A. Ciprofloxacin
B. Clindamycin
C. Doxycycline
D. Gentamicin
Answer and Explanation
B. Clindamycin. Clindamycin, macrolides, chloramphenicol and linezolid act on the 50S subunit. Doxycycline and gentamicin act on the 30S subunit. Ciprofloxacin inhibits DNA gyrase.
Q9. A 6-year-old boy with acute lymphoblastic leukemia develops heart failure after chemotherapy. Which drug is most likely responsible?
A. Cyclophosphamide
B. Doxorubicin
C. Methotrexate
D. Vincristine
Answer and Explanation
B. Doxorubicin. Anthracyclines such as doxorubicin cause dose-dependent dilated cardiomyopathy through free-radical damage. Dexrazoxane can help prevent it. For comparison, cyclophosphamide causes hemorrhagic cystitis and vincristine causes peripheral neuropathy.
Endocrine Drugs
Q10. A 35-year-old woman with weight gain, fatigue and constipation is diagnosed with hypothyroidism and started on levothyroxine. How does this drug work?
A. Blocks TSH secretion
B. Inhibits thyroid peroxidase
C. Replaces deficient thyroid hormone
D. Stimulates iodine uptake
Answer and Explanation
C. Replaces deficient thyroid hormone. Levothyroxine is synthetic T4, which is converted to active T3 in the tissues. The dose is adjusted by checking TSH. Thyroid peroxidase inhibitors (methimazole, PTU) are used for hyperthyroidism.
Q11. A patient on long-term corticosteroid therapy suddenly stops the medication. Which complication is most likely?
A. Adrenal crisis
B. Cushingoid appearance
C. Hyperglycemia
D. Hypertension
Answer and Explanation
A. Adrenal crisis. Long-term steroids suppress the hypothalamic–pituitary–adrenal axis, so the adrenal glands cannot respond quickly when the drug stops. Steroids must be tapered. The other options are effects of taking steroids, not of stopping them.
CNS and Dermatology Drugs
Q12. A 25-year-old man with seizures is taking phenytoin. Which of the following is a well-known side effect of this drug?
A. Pulmonary fibrosis
B. Gingival hyperplasia
C. Hypoglycemia
D. Parkinsonism
Answer and Explanation
B. Gingival hyperplasia. Phenytoin also causes hirsutism, nystagmus and ataxia, megaloblastic anemia (folate deficiency), and is teratogenic (fetal hydantoin syndrome).
Q13. A 23-year-old woman is prescribed isotretinoin for severe cystic acne. What is the most important step before starting therapy?
A. Check for anemia
B. Assess liver function after therapy
C. Screen for TB
D. Perform a pregnancy test
Answer and Explanation
D. Perform a pregnancy test. Isotretinoin is highly teratogenic. Women need two negative pregnancy tests before starting, monthly tests during treatment, and two forms of contraception (the iPLEDGE program in the US). Lipids and liver enzymes are also monitored.
Drug Metabolism
Q14. What is the main action of the pseudocholinesterase (plasma cholinesterase) enzyme?
A. Blocks the secretion of acetylcholine
B. Breaks down acetylcholine at synaptic junctions
C. Competitively inhibits acetylcholinesterase
D. Metabolizes and detoxifies certain drugs
Answer and Explanation
D. Metabolizes and detoxifies certain drugs. Pseudocholinesterase in the plasma breaks down succinylcholine and ester local anesthetics. People with a deficiency can have prolonged paralysis and apnea after succinylcholine. Breaking down acetylcholine at synapses is the job of acetylcholinesterase.
Q15. Some people metabolize drugs slowly by acetylation because of a genetic polymorphism. Which drug is most affected?
A. Clonidine
B. Hydralazine
C. Nitroglycerin
D. Prazosin
Answer and Explanation
B. Hydralazine. Hydralazine, isoniazid and procainamide are metabolized by N-acetylation. Slow acetylators have higher drug levels and a greater risk of drug-induced lupus (and, with isoniazid, peripheral neuropathy).
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