Topiramate Metabolic Acidosis Anaesthesia — FRCA Final MCQ

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ModeratePreoperative AssessmentTopiramate Metabolic Acidosis AnaesthesiaFRCA Final

A 45-year-old woman (ASA II) with chronic migraine is taking topiramate 100 mg BD. She requires general anaesthesia for cholecystectomy. What anaesthetic implication does topiramate have?

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Correct answer: A — Causes prolonged neuromuscular block

Topiramate (carbonic anhydrase inhibitor) causes a non-anion gap (hyperchloraemic) metabolic acidosis by inhibiting renal bicarbonate reabsorption. This is usually mild and compensated, but under anaesthesia (when respiratory compensation may be impaired and further acid loads from surgery/fasting occur), the acidosis may worsen. Pre-operative ABG/venous bicarbonate should be checked. Other anaesthetic implications: topiramate increases the risk of kidney stones (maintain hydration perioperatively), may cause mild cognitive impairment, and has weak carbonic anhydrase inhibitor effects on aqueous humour (relevant if concurrent glaucoma).

Reference: BNF – 2025 – Topiramate: adverse effects; RCOA – 2023 – Drug interactions in anaesthesia