Language Disturbances as Side Effects of Topiramate and Zonisamide Therapy

Reversible side effects of two sulfa-containing antiepileptic drugs (AEDs), topiramate (TPM) and zonisamide (ZNS), are reported. These effects differ from those of other AEDs in that language impairment was the predominant cognitive complaint. Information was available for 42 patients exposed to TPM. Twenty-two (52%) complained of adverse effects; 12, specifically of deficits in language-related functions. Brief neuropsychological testing in four patients on TPM confirmed verbal deficits. These deficits could appear shortly after initiating TPM and disappear variably after drug withdrawal. Similar complaints were seen in a pilot study of ZNS monotherapy, administered in supratherapeutic doses, confirmed by neuropsychological testing. TPM and ZNS both contain a sulfa moiety, suggesting that verbal processing is especially sensitive to these sulfa-containing AEDs.