The acute and steady-state cognitive effects of three new antiepileptic drugs (AED), gabapentin, lamotrigine, and topiramate, were studied in healthy young adults at the University of Alabama Epilepsy Center, Birmingham, AL. Compared with baseline tests of attention and memory, topiramate (TPM) caused statistically significant declines on measures of attention and word fluency at acute doses, whereas gabapentin (GBP) and lamotrigine (LTG) had minimal effects on performance. Only topiramate subjects had persistent neurocognitive impairments when tested after 2 and 4 weeks of drug administration. The TPM group’s verbal fluency rate dropped an average of 50% per subject, and the visual attention task showed a threefold increase in rate of errors. The adverse effects of TPM were not explained by sedation. Mead blood levels by the 4-week test period were within clinical therapeutic ranges: TPM (11 mcg/mL); LTG (8.1); and GBP (9.6). [1]

COMMENT. The adverse effects on cognitive functioning caused by topiramate in healthy young adults have also been observed in patients treated for epilepsy. The potential long-term effects beyond one month were not addressed. Early-onset side effects may subside and may be less evident when the drug is introduced more slowly.