Among the newer anti-seizure drugs, topiramate (Topamax) apparently impairs cognitive performance - to a degree that may affect daily function - whereas gabapentin (Neurontin) seems to have minimal effects on cognition, researchers have shown.

In a study published in the medical journal Neurology, Dr. M. C. Salinsky, of Oregon Health and Sciences University, Portland, and colleagues examined the cognitive effects of topiramate and gabapentin versus placebo in 39 healthy volunteers. The doses were gradually increased over 10 weeks to a maximum of 400 mg per day of topiramate or 3600 mg per day of gabapentin.

The researchers administered cognitive tests at the beginning of the study and after 12 weeks of treatment. A total of 73 healthy subjects were recruited as a comparison group.

Four of six measurements of cognition revealed significant differences between the gabapentin and topiramate groups, Salinsky’s team reports, with the subjects given topiramate having poorer test performance than did the subjects given gabapentin after 12 weeks.

The risk of impaired cognitive function with topiramate “appears to be substantial and is at a level that could have significant adverse effects on daily and occupational functioning,” the researchers note.

However, they also point out that lower doses than those used in the study may be effective for patients with epilepsy and might have a lower risk of cognitive impairment.

SOURCE: Neurology, March 8, 2005.