Once-daily versus twice-daily vigabatrin: is there a difference? The results of a double-blind pilot study

Vigabatrin (VGB) has been approved in Europe and is prescribed for either once or twice-daily administration. This choice has been based on the pharmacodynamic activity of VGB. The purpose of this study was to compare the efficacy and tolerability of these two different medication regimens.

The study design was a double-blind randomized two-period cross-over study in adults who had responded to add-on VGB for previously uncontrolled seizures. Each study period consisted of three months. Patients were maintained on the same daily dose of VGB to which they had demonstrated a clinical response. In addition to the primary efficacy criteria of seizure frequency on the two treatment regimens, this study included blinded ratings of overall efficacy and "well being" by both physician and patient. The primary tolerability criterion was the reported incidence of adverse events by phase.

Fifty patients were initially entered into the study, and 13 patients withdrew before completion, only one reported as due to an adverse event. There was no statistical difference in seizure frequency or the tolerability of the medication. Blinded physician and patient rating scales for seizure control, and patient well being showed a nonstatistical trend toward once-daily administration as compared with twice-daily administration.

This clinical study provides support for the pharmacological evidence that this preparation may be administered on a once or twice daily basis, depending on the individual patient's preference, total dosage and co-medication.