Vigabatrin (Sabril)
Released on to the Australian market in October 1993, Vigabatrin (Sabril) is the first of several new anti-epileptic drugs to be marketed in this country.
How does Vigabatrin work?
Vigabatrin works on a chemical in the brain called GABA. This is one of the chemicals which send messages between nerve cells in the brain. Increasing the amount of GABA helps to reduce the abnormal electrical activity which causes seizures. However, the brain normally breaks down GABA after it has been released. Vigabatrin helps to control seizures by reducing the breakdown of GABA and increasing the amount of this chemical in the brain.
What are its applications?
A number of trials have been conducted to determine the efficacy of this drug. The results have shown that Vigabatrin is often useful in treating seizures which have not been controlled by other medications. There are lots of different types of epilepsy however, and Vigabatrin is not useful for all types. It seems to be most useful in treating partial seizures. Temporal lobe epilepsy, for example, is one common type of epilepsy involving partial seizures. Infantile spasms is one of the main indications in the use of this drug. It also appears to be helpful for children with a particular type of epilepsy called infantile spasms. Vigabatrin is not usually used by itself and is most often added to other medications to help achieve better seizure control.
Benefits for people with epilepsy.
If seizures are not controlled by other available medications, Vigabatrin may be a useful treatment. This will depend on the type of epilepsy however, as not all types may be helped. If seizures are well controlled, there is no reason to change to this drug.
Vigabatrin is taken in capsule form two or three times a day and may be taken with food. There do not appear to be any major interactions with other antiepileptic drugs so existing dosages do not need to be changed when Vigabatrin is started. This drug is not usually measured in the blood, so routine blood level checks are not necessary.
Possible side effects
The most common side effects associated with Vigabatrin are visual field defects, drowsiness and fatigue. It was recently estimated that 10-20% of patients on long-term Vigabatrin will develop visual field constriction. ADRAC recommends that all individuals taking Vigabatrin should have special visual testing at regular intervals. Other side effects (such as depression, weight gain, dizziness, impaired memory, nausea and nervousness) have been a problem for some people and there are other less common side effects. These may occur in up to one in every twenty people. Those with a past history of psychiatric problems may need to be especially careful and should mention this to their doctor.
Some specific groups need to take special care with all new drugs, especially women who are pregnant and/or breast-feeding and people with kidney problems.
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