Topiramate and metabolic acidosis

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