An audit of the new antiepileptic drugs in clinical neurological practice.

Three new antiepileptic drugs (AEDs) are finding increasing use in medical practice. To examine their efficacy and side-effect profile, 483 patients with epilepsy attending either a specialized epilepsy clinic or general neurology clinic under the care of a single consultant neurologist were reviewed. Of these patients 127 had received lamotrigine, 100 vigabatrin and 27 gabapentin. In all but three patients the indication had been epilepsy refractory to other treatments. Efficacy was confirmed if patients achieved a > 50% reduction in seizure frequency or became seizure free. By this criteria 36.3% of patients receiving lamotrigine, 29% receiving vigabatrin and 15% receiving gabapentin benefited significantly. Lack of efficacy was the major reason for discontinuing vigabatrin (27%) and gabapentin (33.3%) whereas an adverse event was the main reason in patients receiving lamotrigine (28.3%). A spectrum of adverse events were noted. Behavioural/psychological effects in particular occurred with all of the drugs and frequently necessitated drug withdrawal. There was also a suggestion of a pharmacodynamic interaction between lamotrigine and both carbamazepine and sodium valproate resulting in toxicity of these latter drugs in a few patients. Drug tolerance was suspected in 12% of patients receiving vigabatrin, less frequently in those on gabapentin and only rarely with lamotrigine.