CNS Pharmacology USMLE Step 1 Practice Question
A 38-year-old woman with chronic migraine headaches takes topiramate 100 mg daily for prophylaxis. She presents with progressive cognitive slowing, memory impairment, and difficulty concentrating over 3 weeks. Vital signs are stable (BP 118/76, HR 76, RR 14, Temp 37°C). Serum bicarbonate is 19 mEq/L. She denies headache improvement. Notably, her symptoms improve on weekends when she skips doses and worsen after resuming medication. Which mechanism best explains this adverse effect?
Answer choices
- AInhibition of monoamine oxidase in the prefrontal cortex
- BCarbonic anhydrase inhibition leading to metabolic acidosis and CNS effectsCorrect answer
- CSodium channel blockade in the cerebral cortex
- DSerotonin antagonism at 5-HT1B receptors
- EGABA-A receptor agonism causing excessive inhibitory tone
- FBlockade of L-type calcium channels in hippocampal neurons
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