Vigabatrin and tiagabine increase GABA concentrations in the central nervous system. This helps to prevent excessive neuronal firing seen in seizures and epilepsy syndromes.
Vigabatrin (brand name Sabril) inhibits GABA degradation by inhibiting GABA transaminase, an enzyme that breaks down GABA. By blocking this function, GABA concentration increases.
Tiagabine (brand name Gabitril) works by inhibiting GABA reuptake into presynaptic neurons. This results in higher synaptic availability of GABA that will be able to bind to receptors on the postsynaptic membrane.
Infantile spasms, also known as West Syndrome, is an epilepsy syndrome of infancy and childhood, most commonly in the first year of life. It is characterized by mental retardation and hypsarrhythmia on interectal EEG. Vigabatrin can be used as monotherapy to treat this condition.
Vigabatrin is used as adjunctive therapy for adult and older pediatric patients with refractory complex partial seizures. Tiagabine is similarly indicated in patients younger than 12 years of age.
Vigabatrin may cause permanent, concentric peripheral visual field loss. The risk is dose-dependent. This is thought to occur from drug-induced injury of retinal photoreceptors, ganglion cells, and their axons. Visual field and ophthalmological testing are needed before treatment and routinely checked every 3 months during treatment. Because of this side effect, this medication is labeled with blackbox warning from the FDA.
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