Positive and negative psychiatric effects of antiepileptic drugs in patients with seizure disorders.

Antiepileptic drugs (AEDs) have various mechanisms of actions and therefore have diverse anticonvulsant, psychiatric, and adverse effect profiles. Two global categories of AEDs are identified on the basis of their predominant psychotropic profiles. One group has "sedating" effects in association with fatigue, cognitive slowing, and weight gain, as well as possible anxiolytic and antimanic effects. These actions may be related to a predominance of potentiation of gamma-aminobutyric acid (GABA) inhibitory neurotransmission induced by drugs such as barbiturates, benzodiazepines, valproate, gabapentin, tiagabine, and vigabatrin. The other group is associated with predominant attenuation of glutamate excitatory neurotransmission and has "activating" effects, with activation, weight loss, and possibly anxiogenic and antidepressant effects. This group includes agents such as felbamate and lamotrigine. Agents such as topiramate, with both GABAergic and antiglutamatergic actions, may have "mixed" profiles. Mechanisms of actions, activity in animal models of anxiety and depression, and clinical psychotropic effects of AEDs in psychiatric and epilepsy patients are reviewed in relationship to this proposed categorization. These considerations suggest the testable hypothesis that better psychiatric outcomes in seizure disorder patients could be achieved by treating patients with baseline "activated" profiles (insomnia, agitation, anxiety, racing thoughts, weight loss) with "sedating" predominantly GABAergic drugs, and conversely those with baseline "sedated" or anergic profiles (hypersomnia, fatigue, apathy, depression, sluggish cognition, weight gain) with "activating" predominantly antiglutamatergic agents. Systematic clinical investigation of more precise relationships of discrete mechanisms of actions to psychotropic profiles of AEDs is needed to assess the utility of this general proposition and define exceptions to this broad principle.