From Felbamate to Carbamazepine: Clinical Consequences of Unintentional Antiepileptic Substitution in Refractory Epilepsy.

Epilepsy is the most common chronic neurological disorder and one of the leading causes of disability. We report a rare and clinically significant complication involving the inadvertent substitution of felbamate with carbamazepine in a 37-year-old man with refractory epilepsy. He developed drowsiness, ataxia, dysarthria, and vomiting, followed by hematological abnormalities and respiratory symptoms. Although carbamazepine levels were within the reference range, a probable diagnosis of acute carbamazepine toxicity was made in the setting of refractory epilepsy. Therapeutic interventions included discontinuation of carbamazepine, antimicrobial therapy, and supportive care. Inadvertent substitution of antiepileptic medications in patients with refractory epilepsy can lead to serious multisystem complications. Vigilant medication management and multidisciplinary care are essential to prevent adverse outcomes.