12 USMLE Pharmacology Quick Review Questions with Answers (Set 10)

These 12 quick USMLE review questions test high-yield facts that show up again and again on the exam: metoclopramide, trimethoprim, methacholine, adrenergic receptors, scopolamine, St. John’s wort, ondansetron, erythromycin, receptor types, hirudin, volume of distribution and amantadine. 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. What is the most effective treatment for gastroparesis in a diabetic patient?

A- Gastric resection
B- Metoclopramide
C- Omeprazole
D- Vagotomy

B- Metoclopramide- Metoclopramide is the most effective treatment for diabetic gastroparesis because it enhances gastric emptying through its prokinetic action.
The correct answer is B

 

Question 2. Which one of the following medications act as bacteriostatic by inhibiting bacterial dihydrofolate reductase?

A- Ciprofloxacin
B- Dapsone
C- Sulfamethoxazole
D- Trimethoprim

D- Trimethoprim- Trimethoprim acts as a bacteriostatic agent by inhibiting bacterial dihydrofolate reductase, an enzyme essential for folate synthesis. This action prevents the synthesis of nucleotides required for DNA replication, thereby halting bacterial growth.
The correct answer is D

 

Question 3. Which one of the following medications stimulates muscarinic receptors in airways when inhaled?

A- Bethanechol
B- Carbachol
C- Methacholine
D- Pilocarpine

C- Methacholine- Methacholine is a muscarinic receptor agonist that stimulates muscarinic receptors in the airways when inhaled. It is primarily used in the methacholine challenge test to diagnose bronchial hyperresponsiveness in conditions like asthma. Inhalation of methacholine causes bronchoconstriction, and the degree of airway narrowing is measured to assess hyperreactivity.
The correct answer is C

 

Question 4. Epinephrine acts on which one of the following receptors to constrict vascular smooth muscle?

A- α1-Adrenoceptors
B- α2-Adrenoceptors
C- β1-Adrenoceptors
D- β2-Adrenoceptors

A- α1-Adrenoceptors- Epinephrine causes vascular smooth muscle constriction primarily by stimulating α₁-adrenergic receptors.
The correct answer is A

 

Question 5. Which of the following is the most prominent side effect of scopolamine?

A- Bradycardia
B- Miosis
C- Mydriasis
D- Profuse sweating

C- Mydriasis- Scopolamine is an anticholinergic drug, and its prominent side effect is mydriasis, often accompanied by blurred vision due to cycloplegia.
The correct answer is C

 

Question 6. Which of the following agents reduces the blood levels of certain drugs through its action on the hepatic P450 system?

A- Grapefruit juice
B- Guava juice
C- Kava
D- St. John’s wort

D- St. John’s wort induces the metabolism of some drugs by stimulation of P450 enzyme activity, while the others inhibit it.
The correct answer is D

 

Question 7. Which of the following receptors is inhibited by ondansetron to treat nausea following chemotherapy?

A- Dopamine receptors
B- Muscarinic receptors
C- Nicotinic receptors
D- Serotonin 5-HT receptors

D- Serotonin 5-HT receptors- Ondansetron is a serotonin 5-HT-receptor antagonist
The correct answer is D

 

Question 8. Which of the following medications may cause acute cholestatic hepatitis?

A- Acarbose
B- Colchicine
C- Erythromycin
D- Metformin
C- Erythromycin-

C- Erythromycin is the only drug on this list that can cause hepatitis while all others can cause diarrhea.
The correct answer is C

 

Question 9. Which of the following types of receptors are associated with the slowest response time?

A- G-protein coupled receptors
B- Ion channel receptors
C- Steroid receptors
D- Transmembrane enzyme receptors

C- Steroid receptors- Response to steroid receptors are measured by days or weeks while other receptors are measured by seconds or minutes.
The correct answer is C

 

Question 10. Which of the following anticoagulant medications works by binding to thrombin and inhibiting it?

A- Heparin
B- Hirudin
C- Ticlopidine
D- Warfarin

B- Hirudin- Hirudin is a direct thrombin inhibitor that binds to thrombin and blocks its activity. Heparin acts indirectly via antithrombin; ticlopidine inhibits platelet aggregation; and warfarin blocks vitamin K-dependent clotting factor synthesis.
The correct answer is B

 

Question 11. Which of the following statements correctly describes the volume of distribution of a drug?

A- It is a kinetic parameter that correlates dose with plasma level of a drug at zero time
B- It is the capacity of a drug to attach to plasma protein
C- It is the concentration of the drug in plasma at a certain time
D- It is the rate of diffusion of the drug through the intracellular component

A- It is a kinetic parameter that correlates dose with plasma level of a drug at zero time. Volume of distribution (Vd) is a theoretical value that relates the amount of drug given to the concentration in plasma at time zero. It does not describe protein binding, plasma concentration at a later time, or diffusion rate.
The correct answer is A

 

Question 12. Which one of the following medications is used for cases of Parkinson’s disease and influenza type A?

A- Amantadine
B- Benztropine
C- Bromocriptine
D- Ribavirin

A- Amantadine- Amantadine is used in Parkinson’s disease to increase dopamine release and decrease reuptake, and it also has antiviral activity against influenza A (though it’s rarely used for flu now due to resistance).
The correct answer is A

 

High-yield points from this set

  • St. John’s wort induces CYP450 and lowers levels of many drugs.
  • Ondansetron blocks 5-HT3 receptors.
  • Erythromycin estolate can cause cholestatic hepatitis.
  • Hirudin and its analogs directly inhibit thrombin.

Keep practicing

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