Vigabatrin Facts
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.
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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.
