Repeated USMLE Questions Step 1 Review- 132- Pharmacology

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Q- Topical benzocaine overuse can cause sudden cyanosis with normal PaO₂. Which one of the following substances can reverse this reaction?

A- Atropine

B- Methylene blue

C- Naloxone

D- Sodium bicarbonate

B- Methylene blue- This is a case of methemoglobinemia from oxidizing agents such as benzocaine or dapsone. Methylene blue is the most effective treatment.

 

Q- A 32-year-old woman with a history of migraines is prescribed sumatriptan. What is its mechanism of action?

A- 5-HT1B/1D receptor agonist

B- 5-HT2 receptor antagonist

C- Dopamine receptor antagonist

D- Voltage-gated calcium channel blocker

A- 5-HT1B/1D receptor agonist- Sumatriptan activates serotonin 5-HT1B/1D receptors, causing vasoconstriction and inhibiting trigeminal nerve activation.

 

Q- A 70-year-old man with atrial fibrillation is prescribed apixaban. What is its mechanism of action?

A- Direct factor IIa (thrombin) inhibitor

B- Direct factor Xa inhibitor

C- Indirect factor Xa inhibitor via antithrombin III

D- Vitamin K epoxide reductase inhibitor

B- Direct factor Xa inhibitor- Apixaban and rivaroxaban directly inhibit factor Xa, reducing thrombin generation and clot formation.

 

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