A 24-year-old woman on broad-spectrum antiepileptic therapy for refractory focal seizures presents with renal colic. Imaging confirms a calcium phosphate kidney stone. She also reports tingling around the mouth. Which drug is most likely responsible for both findings?
- A Topiramate ✓
- B Oxcarbazepine
- C Zonisamide
- D Rufinamide
Correct answer: A. Topiramate
Explanation
Topiramate inhibits carbonic anhydrase, producing mild metabolic acidosis and alkaline urine that favours calcium phosphate stone formation; paraesthesias are another expression of this enzyme inhibition. Zonisamide also contains a sulfonamide moiety and shares some carbonic anhydrase activity, but nephrolithiasis is classically linked to topiramate and acetazolamide. Oxcarbazepine causes hyponatraemia rather than stones.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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