Effect of antiepileptic drugs on cognitive function in individuals with epilepsy: a comparative review of newer versus older agents.

Several 'new' antiepileptic drugs (AEDs), i.e. oxcarbazepine, vigabatrin, lamotrigine, zonisamide, gabapentin, tiagabine, topiramate and levetiracetam have been introduced into clinical practice within the last decade. Most of these new drugs are at least as effective as the 'old' AEDs [phenytoin, phenobarbital (phenobarbitone), valproic acid (sodium valproate) and carbamazepine] and, in general, they seem to be better tolerated than the old drugs. The new AEDs might have less influence on cognitive functions but the aspect has not been systematically studied. 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. Alteration of cognition might reflect a chronic adverse effect of AEDs but the negative effects of the drugs are only one of several factors that may influence cognition. In addition, subjective complaints about cognitive deficits (e.g. memory problems or attention) may also reflect other aspects of adverse effects than those concerning specific cognitive functions (e.g. mood and anxiety). 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. In general, the new AEDs seem to display no or minor negative cognitive effects. In studies in which new AEDs have been compared with old AEDs, there was a tendency in favour of the new AEDs in some of the studies.