Multicenter long-term safety and efficacy study of vigabatrin for refractory complex partial seizures: an update. We followed 66 patients with refractory complex partial seizures and a favorable initial response to vigabatrin for 5 to 72 (median, 43) months. Thirty-seven patients discontinued vigabatrin for the following reasons: benefit-to-risk evaluation, 8; seizure breakthrough, 6; adverse events, 6; seizure breakthrough and adverse events, 5; moved or lost, 4; no longer eligible for study, 2; non-drug-related death, 2; narcotic abuse, 1; and patient request, three. There were no clinically significant abnormalities in laboratory studies including SMA 12, complete blood count, ECG, EEG, and visual evoked response testing, and no toxicity other than reversible, dose-dependent side effects. Based on this and other long-term data, clinical trials of vigabatrin have resumed in the United States and Canada. 