Vigabatrin Side Effects, Dosage & Cost
What is a seizure?
A seizure is an abnormal and unregulated electrical impulse that happens in the brain’s cortical gray matter. It temporarily interrupts normal brain function. It usually causes altered awareness of circumstances, unusual sensations, focal involuntary movements or spasms and involuntary contraction of voluntary muscles. About 2% of adults have a seizure at some point during their life, two thirds of that 2% never have a second one.
What is Vigabatrin?
Vigabatrin is an anticonvulsant that acts as an inhibitor to the catabolism (metabolism) of GABA, a brain chemical. It’s a similar chemical to GABA, but isn’t a receptor agonist, (a chemical that binds to a receptor and activates the receptor to produce a biological response). The mechanism of its action is that it’s an irreversible inhibitor of gamma–aminobutyric 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 and it’s believed seizures are the result of low levels of this chemical.
Vigabatrin is manufactured and distributed by Lundbeck Inc. (formerly Ovation Pharma). Sabril is a commonly used brand name.
What is the History of Vigabatrin?
As of 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 August 2009. Under the name Sabril, it was the first drug approved to treat infantile spasms in the US. It had previously 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 it 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, the loss is in the peripheral vision, had been noticed as early as 1997. 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) and because of this risk, it’s available only through a restricted distribution.
Other side effects can include headache, fatigue, dizziness, drowsiness first day of use. Less reported are weight gain, nervousness, hyperactivity, depression, nausea, constipation or 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 made 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.