Vigabatrin is an analogue of gamma aminobutayric acid and belongs to a group of drugs known as anticonvulsant drugs but it is chemically unrelated to other anticonvulsant drugs.It can be prescribed in combination with other drugs for focal epilepsy with or without secondary generalization.It is also used in partial seizures and as a monotherapy in the treatment of infantile spasm in west's syndrome.
Vigabatrin half life is approximately 6-8 hours but considerable evidence suggest that pharmacodynamic activity of the drug is more prolonged and not well correlated with the plasma half life.
Mechansim Of Action:
Vigabatrin inhibits irreversibly the enzyme GABA aminotransferase ( enzyme causing metabolism of GABA),Thus, increasing the concentration of GABA at its synapses. It may also work by suppressing repetitive neuronal firing through blocking of voltage-sensitive sodium channels.
More common Side effects of Vigabatrin include drowsiness,dizziness, weight gain while less common side effects include confusion, agitation and psychosis.Its prolonged administration may cause visual field defects in about 1/3rd of persons.Due to this adverse effect it is rarely used currently.This drug was delayed in its world wide introduction by the appearance of a reversable intramyelinic edema in the rats and dogs.
Caution should to be taken in elderly( Closely monitor neurological function), avoid sudden withdrawal, in depression, absence seizure, history of psychosis, and it is also contraindicated in visual field defects.Avoid Vigabatarin if you are allergic to this drug or any other part of this drug.
Vigabatrin is The U.S. Food and Drug Administration (FDA) Pregnancy Category C drugs , known to cause birth defects in animals, and suspected to be able to produce birth defects in people. Talk to your doctor or another health professional if you are pregnant or plan to become pregnant.
- Initially 1 g per day in a single dose or 2 divided doses then increased according to response in step of 500 mg at weekly intervals.usual range 2-3g per day not more than 3 g daily.
- Dose for Child initially 40mg/kg body weight over 35 kg ,maximum 1 g) daily in a single dose or divided doses.then adjusted according to response .usual maintenance dose for body weight 10-15kg , 0.5-1g per day.body weight 15-30kg ,1-1.5g per day.body weight 30-50kg ,1.5g per day body wirght over 50kg,2-3g per day.
- Dose for infantile spasm mono-therapy 50mg/kg,adjusted according to response over 7 days, increase dose upto 150 mg if tolerated.