Cognitive Effects of Newer Antiepileptic Drugs

Lee, Sang Ahm

Abstract

People with epilepsy are at increased risk of cognitive impairment as a result of multiple factors:the underlying etiology of epilepsy, the effects of seizures themselves, and the central nervous system effects of antiepileptic drugs (AEDs). Cognitive effects of AEDs are of special concern because AEDs are the major therapeutic modality for seizures. All commonly used AEDs have some effect on cognitive function. The risk of AEDs cognitive adverse effects is increased with polypharmacy and at higher dosages and higher AED blood levels. Also children and the elderly are especially vulnerable to adverse effects on cognition. The most common AED cognitive effects include psychomotor slowing, reduced vigilance, and impairments in memory. This review focuses on studies of the cognitive effects of the new AEDs, and in particular on studies that compare cognitive effects of the old and new drugs. The available evidence is insufficient to support definite conclusions about the cognitive effects of the new AEDs. Neuropsychological testing has been the major method of objectively examining cognitive function related to the use of AEDs but a number of methodological problems blur the results. However, some of the new AEDs appear to produce fewer adverse cognitive effects than the old AEDs. Lamotrigine, for which a relatively large number of studies are available, has demonstrated a favorable cognitive profile overall, both in volunteers and in patients with epilepsy. Oxcarbazepine appears not to affect cognitive function in healthy volunteers or adults with newly diagnosed epilepsy. Gabapentin, tiagabine, and vigabatrin also have shown few cognitive effects compared with placebo. Although dose and titration speed may be confounding factors in some of the studies of topiramate, there is clear evidence that this agent does affect cognitive function, with specific effects on attention and verbal function. Additional studies are needed to delineate fully the relative effects of all the new AEDs to each other and to the older AEDs.