Vigabatrin Side Effects, Dosage & Cost
What is a seizure?
Seizures, convulsions or fits, are caused by periods of disturbed brain function. They can alter behavior or attention span. Abnormally excited electrical impulses in the brain cause these episodes, whether mild and of short duration , or longer and with more effect on the individual.
What is Vigabatrin?
Vigabatrin is an anticonvulsant that acts as an inhibitor to the catabolism (metabolism) of GABA. It’s a similar chemical to GABA, but isn’t a receptor agonist. The mechanism of its action is that it’s an irreversible inhibitor of gamma–amino butyric acid and transaminase (GABA–T), which is the enzyme responsible for the metabolism of GABA. That enzyme increases the level of GABA in the nerve synapses. In essence Vigabatrin increases the amount of GABA, a brain chemical. It’s believed seizures are the result of low levels of this chemical, GABA.
Vigabatrim is manufactured and distributed by Lundbeck Inc. (formerly Ovation Pharma). Sabril is a commonly used brand name.
What is the History of Vigabatrin?
In December 2006 administration of Vigabatrin appeared to control infantile spasms, one of the forms of catastrophic epilepsy. It was a drug widely used worldwide but not approved in the US until Aug. 2009. Under the name Sabril, it is the first drug in the US approved to treat infantile spasms. It previously had been approved in the US for adult use in combination with other medications for the treatment of complex partial seizures that didn’t respond satisfactorily to other drug therapy.
What are Common Vigabatrin Side Effects?
The main safety concern with the use of Vigabatrin is vision damage. In 2003 is was shown to cause irreversible diffuse atrophy of the retinal nerve fiber layer. This was discovered in a retrospective study involving 25 subjects. It had the most effect on the outer area as opposed to the macular or central area of the retina. Visual defects had been noticed as early as 1997. The loss is in the peripheral vision. The risk increases with higher dosage and longer duration of use, though even a low dose can cause visual damage. Regular vision testing is required for those on Vigabatrin (Sabril). Because of this risk, it’s available only through a restricted distribution.
Other side effects can include headache, fatigue, dizziness, drowsiness in the first day. Less reported effects are weight gain, nervousness, hyperactivity, depression, nausea or constipation, stomach upset. If these become lasting and bothersome, consult your physician. Your doctor should immediately be notified if a rash develops, vision changes, clumsiness or behavior changes occur, depression or seizures develop.
Your doctor should be aware if you have a history of nervous, emotional or mental problems, allergies or kidney disease. Alcohol should be avoided while taking Vigabatrin and it shouldn’t be taken during pregnancy.
What is the Average Vigabatrin Dosage and Cost?
Vigabatrin comes in powder and tablet form.
In powder form, for infantile seizures, body weight will determine the dosage. The common dose is 50 to 100 mg per kg. (22.7 to 45.5 mg per pound) of body weight per day. It’s given in smaller doses twice a day. The most effective results occur when this medication is evenly spaced throughout the day to ensure constant levels in the body. It can be taken before or after meals. It shouldn’t be abruptly stopped without your doctor’s consent.
For children, the powder is also based on body weight. A recommended beginning dose is 40 mg per pound. The dose shouldn’t be increased to more than 100 mg per pound of body weight daily, taken in two smaller doses.
Adults should start with 1000 mg a day, not to exceed 4000 mg daily.
The dosages for tablets are similar. If a dose is missed, it should be taken as soon as possible. If it’s nearly time for the next dose, the missed one should be skipped. Don’t double dose.
The cost of Vigabatrin is about $1.60 per 500 mg tablet.