Vigabatrin

What it is and how it works

Mechanism of Action The precise mechanism of vigabatrin’s anti-seizure effect is unknown, but it is believed to be the result of its action as an irreversible inhibitor of γ-aminobutyric acid transaminase (GABA-T), the enzyme responsible for the metabolism of the inhibitory neurotransmitter GABA. This action results in increased levels of GABA in the central nervous system. No direct correlation between plasma concentration and efficacy has been established. The duration of drug effect is presumed to be dependent on the rate of enzyme re-synthesis rather than on the rate of elimination of the drug from the systemic circulation.

Indications

Vigabatrin for oral solution is indicated for the treatment of: Refractory Complex Partial Seizures as adjunctive therapy in patients 2 years of age and older who have responded inadequately to several alternative treatments; vigabatrin for oral solution is not indicated as a first line agent Infantile Spasms - monotherapy in infants 1 month to 2 years of age for whom the potential benefits outweigh the potential risk of vision loss Refractory Complex Partial Seizures (CPS) Vigabatrin for oral solution is indicated as adjunctive therapy for adults and pediatric patients 2 years of age and older with refractory complex partial seizures who have inadequately responded to several alternative treatments and for whom the potential benefits outweigh the risk of vision loss . Vigabatrin for oral solution is not indicated as a first line agent for complex partial seizures.

Dosage and administration (summary)

Refractory Complex Partial Seizures Adults (17 years of age and older): Initiate at 1,000 mg/day (500 mg twice daily); increase total daily dose weekly in 500 mg/day increments, to the recommended dose of 3,000 mg/day (1,500 mg twice daily) Pediatric (2 to 16 years of age): The recommended dosage is based on body weight and administered as two divided doses The dosage may be increased in weekly intervals, depending on response Dose patients weighing more than 60 kg according to adult recommendations Infantile Spasms Initiate at a daily dose of 50 mg/kg (25 mg/kg twice daily).

Contraindications

None. None

Warnings and precautions

Abnormal MRI signal changes and intramyelinic edema have been reported in some infants with Infantile Spasms receiving vigabatrin ( 5.3 , 5.4 ) Suicidal behavior and ideation: Antiepileptic drugs, including vigabatrin, increase the risk of suicidal thoughts and behavior Withdrawal of AEDs: Taper dose to avoid withdrawal seizures Anemia: Monitor for symptoms of anemia Somnolence and fatigue: Advise patients not to drive or operate machinery until they have gained sufficient experience on vigabatrin Permanent Vision Loss Vigabatrin can cause permanent vision loss.

Pregnancy

Pregnancy Pregnancy Exposure Registry There is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to AEDs, including vigabatrin, during pregnancy. Encourage women who are taking vigabatrin during pregnancy to enroll in the North American Antiepileptic Drug (NAAED) Pregnancy Registry.

Storage and supply

How Supplied Vigabatrin for oral solution USP, 500 mg packets contain a white to off-white granular powder. They are available as follows: Carton of 50 packets: NDC 69238-1425-5 (Single Packet: NDC 69238-1425-1) The oral syringes are provided separately by the pharmacy. Storage and Handling Store at 20° to 25°C (68° to 77°F) .

Source: Vigabatrin (Vigabatrin) — US FDA prescribing information, 2022-12-23, DailyMed. Summarised and shortened; the full label governs. Iranian registration, indications and labelling may differ.