Vigabatrin (5 brand names, 3 dosage forms, 1 route)
Available dosage forms: TABLET, FOR SOLUTION, SOLUTION.
Routes of administration: ORAL.
Brand Names
- SABRIL
- VIGABATRIN
- VIGADRONE
- VIGAFYDE
- VIGPODER
Boxed Warning
Vigabatrin can cause permanent bilateral concentric visual field constriction, including tunnel vision that can result in disability. In some cases, vigabatrin also can damage the central retina and may decrease visual acuity [see Warnings and Precautions (5.1)]. The onset of vision loss from vigabatrin is unpredictable, and can occur within weeks of starting treatment or sooner, or at any time after starting treatment, even after months or years. Symptoms of vision loss from vigabatrin are unlikely to be recognized by patients or caregivers before vision loss is severe. Vision loss of milder severity, while often unrecognized by the patient or caregiver, can still adversely affect function. The risk of vision loss increases with increasing dose and cumulative exposure, but there is no dose or exposure known to be free of risk of vision loss. Vision assessment is recommended at baseline (no later than 4 weeks after starting vigabatrin), at least every 3 months during therapy, and about 3 to 6 months after the discontinuation of therapy. Once detected, vision loss due to vigabatrin is not reversible. It is expected that, even with frequent monitoring, some patients will develop severe vision loss. Consider drug discontinuation, balancing benefit and risk, if vision loss is documented. Risk of new or worsening vision loss continues as long as vigabatrin is used. It is possible that vision loss can worsen despite discontinuation of vigabatrin. Because of the risk of vision loss, vigabatrin should be withdrawn from patients with refractory complex partial seizures who fail to show substantial clinical benefit within 3 months of initiation and within 2 to 4 weeks of initiation for patients with infantile spasms, or sooner if treatment failure becomes obvious. Patient response to and continued need for vigabatrin should be periodically reassessed. Vigabatrin should not be used in patients with, or at high risk of, other types of irreversible vision loss unless the benefit
Contraindications
None.
Adverse Reactions
The following serious and otherwise important adverse reactions are described elsewhere in labeling: Permanent Vision Loss [see BOXED WARNING and Warnings and Precautions (5.1)] Magnetic Resonance Imaging (MRI) Abnormalities in Infants [see Warnings and Precautions (5.3)] Neurotoxicity [see Warnings and Precautions (5.4)] Suicidal Behavior and Ideation [see Warnings and Precautions (5.5)] Withdrawal of Antiepileptic Drugs (AEDs) [see Warnings and Precautions (5.6)] Anemia [see Warnings and Precautions (5.7)] Somnolence and Fatigue [see Warnings and Precautions (5.8)] Peripheral Neuropathy [see Warnings and Precautions (5.9)] Weight Gain [see Warnings and Precautions (5.10)] Edema [see Warnings and Precautions (5.11)]
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.