8 USMLE Pharmacology Quick Review Questions with Answers (Set 42)

These 8 quick USMLE pharmacology review questions cover the mechanisms, side effects and uses of thiazides in gout, clindamycin, rifampin and warfarin, carvedilol, carbamazepine, propranolol, omeprazole, albuterol and warfarin skin necrosis. Each question includes the correct answer.

Written by Dr. Ray Makar, MD, author of the Repeated USMLE Questions eBook series.

Prefer video? Watch daily USMLE case questions on MedFocus by Dr. Ray on YouTube.

How to use this page: read the question, pick your answer, then tap Show Answer and Explanation.

Questions

Question 1. Which of the following antibiotics is most likely to cause pseudomembranous colitis due to Clostridium difficile?

A- Ampicillin
B- Ciprofloxacin
C- Clindamycin
D- Erythromycin

C- Clindamycin- It is strongly associated with C. difficile-associated diarrhea by disturbing normal gout flora.
The correct answer is C

 

Question 2. A patient on warfarin starts rifampin for TB. Which of the following happens to warfarin’s effect?

A- Decreased effect due to CYP induction
B- Increased effect due to CYP inhibition
C- No effect on drug metabolism
D- Unpredictable effect on drug levels

A- Decreased effect due to CYP induction- Rifampin induces CYP450 enzymes, increasing warfarin metabolism and reducing its anticoagulant effect-risk of thrombosis.
The correct answer is A

 

Question 3. Which of the following best describes the mechanism of action of carvedilol in treating high blood pressure?

A- Calcium channel blocker in vascular smooth muscle
B- Central α₂-adrenergic stimulation
C- Nonselective β-adrenergic blockade with α₁-adrenergic blockade
D- Selective β₁-adrenergic blockade only

C- Carvedilol is a nonselective β-blocker (β₁ and β₂) with additional α₁-blocking activity. β-blockade decreases heart rate, myocardial contractility, and renin release. α₁-blockade causes peripheral vasodilation, reducing systemic vascular resistance. This combined effect lowers both cardiac output and total peripheral resistance, making it effective for hypertension and heart failure.
The correct answer is C

 

Question 4. Which of the following best describes the mechanism of action of carbamazepine in treating trigeminal neuralgia?

A- Blockade of N-type calcium channels in presynaptic neurons
B- Blockade of voltage-gated sodium channels, reducing neuronal firing
C- Enhancement of GABA-A receptor activity
D- Inhibition of serotonin reuptake in the brain

B- Carbamazepine is an antiepileptic drug that works by blocking voltage-gated channels in neuronal membranes. This action stabilizes the inactivated state of the sodium channel, preventing repetitive and high-frequency firing of action potentials. In trigeminal neuralgia, this dampens ectopic discharges in the trigeminal nerve, relieving the severe facial pain.
The correct answer is B

 

Question 5. Which of the following best describes the mechanism of action of propranolol in treating essential tremors?

A- Enhancement of GABAergic neurotransmission in the CNS
B- Nonselective β-adrenergic blockade reduces peripheral β₂-mediated activity
C- Selective β₁-adrenergic blockade decreases heart rate
D- Stimulation of β₂-adrenergic receptors in skeletal muscle

B- Propranolol is a nonselective β-blocker that inhibits both β₁ and β₂ adrenergic receptors. In essential tremor, blocking β₂ receptors in skeletal muscle reduces the sensitivity of muscle spindles and dampens tremor amplitude. This mechanism is peripheral and not primarily CNS-mediated.
The correct answer is B

 

Question 6. A 64-year-old man with atrial fibrillation is started on warfarin therapy. After 3 days, he develops skin necrosis. Which of the following best explains this complication?

A- Direct inhibition of thrombin
B- Immediate depletion of clotting factors II, VII, IX, X
C- Rapid decline in protein C leading to transient hypercoagulability
D- Vitamin K deficiency before therapy

C- Rapid decline in protein C leading to transient hypercoagulability- Warfarin inhibits vitamin K-dependent factors and protein C and S. Since protein C has a short half-life, it falls quickly, causing a temporary hypercoagulable state and skin necrosis in some patients.
The correct answer is C

 

Question 7. A 40-year-old man with peptic ulcer disease is started on omeprazole. Which of the following is the primary mechanism of action of this medication?

A- Blocks H₂ receptors on gastric parietal cells
B- Irreversibly inhibits the H⁺/K⁺-ATPase pump in parietal cells
C- Neutralizes gastric acid by chemical reaction
D- Stimulates prostaglandin receptors in the gastric mucosa

B- Irreversibly inhibits the H⁺/K⁺-ATPase pump in parietal cells- Omeprazole is a proton pump inhibitor (PPI) that irreversibly blocks the H⁺/K⁺ ATPase in gastric parietal cells, leading to a profound reduction in gastric acid secretion.
The correct answer is B

 

Question 8. A 25-year-old woman with asthma presents to the emergency department with shortness of breath. She is given an inhaled medication that acts by stimulating β₂-adrenergic receptors, leading to smooth muscle relaxation in the bronchi. Which of the following drugs was most likely administered?

A- Albuterol
B- Ipratropium
C- Propranolol
D- Theophylline

A- Albuterol- Albuterol is a short-acting β₂-adrenergic agonist used for rapid relief of acute bronchospasm in asthma.
The correct answer is A

 

High-yield points from this set

  • Thiazides can worsen gout by raising uric acid.
  • Clindamycin is strongly associated with C. difficile colitis.
  • Rifampin induces CYP450 and lowers warfarin’s effect.
  • Warfarin skin necrosis is caused by an early drop in protein C.

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