• Metabolism: Almost no metabolic transformation. Does not induce the hepatic cytochrome P450 system. Route of Elimination: Eliminated primarily through renal excretion as unchanged drugs (80%). Half Life: Neonates, 50 mg/kg = 7.5 ± 2.1 hours (due to reduced renal function); Infants = 5.7 hours; Adults = 7.5 hours; Elderly = 12 - 13 hours
• Uses/Sources: For use as an adjunct in treatment resistant epilepsy, refractory complex partial seizures, and secondary generalized seizures. It is also used as monotherapy in infantile spasms in West syndrome.
• Health Effects: May cause a potentially dangerous rash that may develop into Stevens Johnson syndrome, an extremely rare but potentially fatal skin disease.
• Route of Exposure: Rapidly absorbed following oral administration, absorption is comparable between neonates, infants, and children. Cmax, 50 mg/kg dose, neonates= 14 mg/L; Tmax, 50 mg/kg dose, neonates = 2.1 hours; However, extent of absorption is higher and elimination half life is longer in neonates compared to children and infants. This is because neonates have reduced renal function compared to the aforementioned population groups. AUC, 50 mg/kg dose, neonates = 142.6 ± 44.0 mg/L/hr; Food may slightly decrease the rate (Cmax decreased by 33%, Tmax increased to 2 hours), but not the extent of absorption. Furthermore, vigabatrin does not cross the blood-brain-barrier well, thus high doses are needed.

• Carcinogenicity: No indication of carcinogenicity to humans (not listed by IARC).
• Toxicity: LD50, oral, rat: 3000 mg/kg

Vigabatrin increases brain concentrations of gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter in the CNS, by irreversibly inhibiting enzymes that catabolize GABA (gamma-aminobutyric acid transaminase, GABA-T). Duration of action is determined by rate of GABA-T re-synthesis. Vigabatrin may also work by suppressing repetitive neuronal firing through inhibition of voltage-sensitive sodium channels. Although administered as a racemic mixture, only the S(+) enantiomer is pharmacologically active.