Topiramate and metabolic acidosis.

Topiramate (TPM) is a novel antiepileptic medication (AED) with at least three mechanisms of action. A possible fourth mechanism, that of a carbonic anhydrase inhibitor, also may contribute to its antiepileptic properties. We report a patient with intractable epilepsy and normal renal function who developed a normal anion gap metabolic acidosis, which worsened during elective surgery for temporal lobectomy. We believe this side effect of TPM can become clinically significant during surgery, concomitant use of another carbonic anhydrase inhibitor, and potentially with the ketogenic diet.