Vigabatrin is a prescription medication utilized in the treatment of specific seizure disorders. It is classified as an antiepileptic drug, working to manage uncontrolled electrical activity in the brain that leads to seizures. This medication is available in various forms, including tablets, oral solutions, and powder packets, to suit different patient needs.
Approved Medical Applications
Vigabatrin is approved by the U.S. Food and Drug Administration (FDA) for two distinct seizure conditions: infantile spasms and refractory complex partial seizures.
Infantile spasms are a severe form of epilepsy that typically affects infants between one month and two years of age. These seizures manifest as sudden, brief contractions of the head, trunk, and limbs, often occurring in clusters. This condition is associated with a poor prognosis, including potential neurodevelopmental regression.
For infantile spasms, vigabatrin is approved as a monotherapy, meaning it can be used as the sole treatment. Its approval for this condition came on August 21, 2009.
Refractory complex partial seizures, also known as focal onset impaired awareness seizures, are another indication for vigabatrin. “Refractory” indicates that these seizures have not responded adequately to several other anti-seizure medications. Vigabatrin is approved as an adjunctive therapy for these seizures, meaning it is used in combination with other medications. Initially approved for patients 10 years and older, the FDA expanded its indication in January 2020 to include individuals aged 2 to 10 years.
How Vigabatrin Works
Vigabatrin’s action centers on increasing the levels of gamma-aminobutyric acid (GABA), a calming chemical in the brain. GABA is the primary inhibitory neurotransmitter in the central nervous system, meaning it helps to reduce excessive electrical activity and dampen overactive neuronal firing.
The medication achieves this by irreversibly inhibiting GABA transaminase (GABA-T), an enzyme responsible for breaking down GABA and reducing its concentration. When vigabatrin blocks GABA-T, less GABA is broken down, leading to an accumulation in the synaptic clefts—the spaces between nerve cells where chemical signals are transmitted. This sustained increase in GABA levels enhances the brain’s natural inhibitory processes.
Important Safety Considerations
Vigabatrin carries safety considerations, particularly concerning the risk of permanent vision loss. This medication can cause bilateral concentric visual field constriction, a narrowing of peripheral vision sometimes described as “tunnel vision.” It can also damage the central retina, potentially decreasing visual acuity. The onset of this vision loss is unpredictable and can occur at any point during treatment, even after months or years, and may not be noticed by patients or caregivers until it is severe.
Due to this risk, vigabatrin is available only through a restricted program. Patients need regular eye examinations: within four weeks of starting, at least every three months during treatment, and three to six months after stopping. While these tests cannot prevent vision damage, they are important for early detection to help prevent further damage by prompting discontinuation. Once vision loss is detected, it is generally not reversible.
Other common side effects include drowsiness, dizziness, fatigue, and weight gain. Patients may also experience problems with coordination, memory issues, and swelling of the hands or feet. Less common but serious side effects can include depression, suicidal thoughts or behavior, and peripheral neuropathy, which can cause numbness or tingling. Healthcare providers should monitor for changes in mood or behavior. It is important not to suddenly stop taking vigabatrin, as this can worsen seizures.