Felbamate monotherapy has stimulant-like effects in patients with epilepsy

The objective of this study was to assess the psychiatric effects of the antiepileptic drug (AED) felbamate (FBM) in patients with epilepsy. FBM is a new AED with a novel putative (antiglutaminergic) mechanism. Older AEDs such as carbamazepine and valproate have psychotropic properties, but the psychiatric effects of FBM and other new antiglutamatergic AEDs remain to be determined. Thirty inpatients with refractory epilepsy were openly tapered off all AEDs in conjunction with intensive presurgical monitoring prior to a two week randomized double-blind parallel trial of FBM monotherapy versus placebo, followed by open FBM therapy. Psychopathology was rated with weekly psychiatric rating scales. Anxiety, depression and seizures increased significantly with AED discontinuation. Acute blind FBM monotherapy yielded antiepileptic and stimulant-like effects (insomnia, anorexia, and anxiety), but failed to influence AED withdrawal-emergent psychopathology. Restarting original AEDs resolved such pathology in FBM drop outs. Chronic open FBM also had stimulant-like effects, with half of the patients displaying psychiatric deterioration and the other half modest improvement compared to baseline therapies. Baseline insomnia and anxiety may be markers for poorer psychiatric responses to chronic open FBM. FBM had stimulant-like effects, lacked anxiolytic effects, and failed to attenuate AED withdrawal-emergent psychopathology. Baseline insomnia or anxiety may predict poorer psychiatric responses to FBM. Further studies are required to assess whether the novel psychiatric effects observed with FBM also occur with other new antiglutamatergic AEDs.