Vigabatrin has not been approved by the Food and Drug Administration (FDA) in the United States, but it has been available in other countries for many years. Vigabatrin is mainly used to treat complex partial and secondarily generalized tonic-clonic seizures. It is also used to treat infantile spasms and seizures in patients with Lennox-Gastaut syndrome.
Vigabatrin was developed by a research laboratory in France in 1977. Unlike many other seizure medicines discovered by accident, vigabatrin was purposely developed with a specific plan in mind— to prevent the breakdown of GABA, a neurotransmitter that inhibits brain activity. Vigabatrin was first marketed in Europe in the late 1980s and was approved in Australia in 1993 and in Canada in 1994.
In April, 2004, Ovation Pharmaceuticals announced that it had arranged to buy the North American rights to vigabatrin and planned to try to get FDA approval for sale in the United States.
Unfortunately, as many as 25% of patients who take vigabatrin suffer damage to the retina of the eye, limiting the field of vision. Because of this safety issue, the FDA has refused to approve vigabatrin. Because of the lack of FDA approval, vigabatrin is used rarely in the United States, most often in children with infantile spasms that do not respond to other medications.
Vigabatrin is generally well tolerated and typically has few unwanted side effects.
In a study of more than 2000 adults, the two most common side effects were drowsiness (12.5%) and fatigue (9%). Other rare side effects include:
The side effect most often mentioned in children taking vigabatrin is hyperactivity, which was occurred in 11% of 299 children in one study. These children were also taking other seizure medicines at the same time, making it possible that the hyperactivity was not due to vigabatrin alone.
Finally, occasional patients can experience an increase in their seizures after starting vigabatrin, particularly patients with myoclonic seizures.
Most people who take vigabatrin have no or few side effects that fade within a short period of time. But a few people have serious reactions. The best-known serious problem with vigabatrin is irreversible damage to the retina of the eye, causing a visual-field defect in up to 25% of people who have been taking vigabatrin for a long time. This potential problem may be a reason not to use vigabatrin if there are good alternatives. If you do use vigabatrin, you should have regular examinations to detect early signs of damage.
Warning signs of other serious problems include:
If you notice any of these symptoms, call your doctor immediately, but do not stop taking or change the dose of vigabatrin without first consulting your doctor.
The psychiatric effect of vigabatrin requires further study. The incidence of depression and psychotic reactions in patients taking vigabatrin is not high but may be slightly higher than in other patients with epilepsy. These disorders are probably more likely to occur in patients who have a history of psychiatric illness. In past studies, they have generally disappeared when the medication was stopped.
Vigabatrin is effective in treating a wide variety of seizures, but when used for some disorders, it is possible that vigabatrin can exacerbate seizures. Patients with generalized seizures, including tonic-clonic seizures and myoclonic seizures, should be aware of this risk. In one fairly small study, 20% of children with refractory epilepsy experienced a seizure increase. Further study is needed to determine how much of this effect is just due to chance.
As with many other seizure medicines, there is a very small chance of developing a rash so serious that hospitalization may be required. Though the risk is small, call the doctor promptly if you notice a rash, since in a few cases these rashes are dangerous and could be fatal.
Anyone with an allergy to vigabatrin should not take it. People with psychiatric disease should be careful about taking vigabatrin.
The good news about vigabatrin is that it neither affects, nor is affected by, other medicines.
Since vigabatrin is not approved for use by the FDA in the United States, our experience with women taking it during pregnancy is limited. Further, when vigabatrin is used in the US, it is usually only in very severely affected patients, in whom pregnancy is usually best avoided.