Vigabatrin is an irreversible inhibitor of the enzyme γ-aminobutyric acid (GABA) transaminase (GABA-T) and is marketed in >20 countries, including Canada but not the U.S.A., as an antiepileptic drug. Vigabatrin has demonstrated considerable efficacy against complex partial and secondarily generalized tonic-clonic seizures in patients refractory to conventional antiepileptic drugs. The most common side effects of vigabatrin are drowsiness, irritability, ataxia, dizziness, and headache. Behavioral disturbances are a rare and reversible side effect. The drug has no known systemic or irreversible side effects. The time course of action of vigabatrin depends principally upon regeneration of GABA-T inactivated by the drug.