indication

For use as an adjunctive treatment (with other drugs) in treatment resistant epilepsy, complex partial seizures, secondary generalized seizures, and for monotherapy use in infantile spasms in West syndrome.

pharmacology

Vigabatrin, is an anticonvulsant chemically unrelated to other anticonvulsants. Vigabatrin inhibits the catabolism of GABA. It is an analog of GABA, but it is not a receptor agonist. Vigabatrin irreversibly inhibits the enzyme GABA transaminase.

mechanism of action

It is believed that 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) or block the reuptake of GABA into glia and nerve endings. Vigabatrin may also work by suppressing repetitive neuronal firing through inhibition of voltage-sensitive sodium channels.

biotransformation

Almost no metabolic transformation. Does not induce the hepatic cytochrome P450 system.

absorption

Rapidly absorbed following oral administration. Food may slightly decrease the rate, but not the extent, of absorption.

half life

5-8 hours in young adults, 12-13 hours in elderly.

route of elimination

Vigabatrin is not significantly metabolized; it is eliminated primarily through renal excretion.

drug interactions

Fosphenytoin: Vigabatrin decreases the effect of hydantoin

Mefloquine: Mefloquine may decrease the serum concentration of Vigabatrin. This may increase the risk of seizure in patients receiving Vigabatrin to prevent seizures. Consider alternate therapy or monitor for changes in Vigabatrin serum concentration, therapeutic or adverse effects if Mefloquin is initiated, discontinued or dose changed.

Methotrimeprazine: Additive CNS depression may occur. Dose adjustments may be required if one agent is added to existing therapy with the other agent. Monitor for increased CNS depression during concomitant therapy.

Phenytoin: Vigabatrin decreases the effect of hydantoin

Triprolidine: The CNS depressants, Triprolidine and Vigabatrin, may increase adverse/toxic effects due to additivity. Monitor for increased CNS depressant effects during concomitant therapy.