Sabril (vigabatrin) for Complex Partial Seizures (CPS)

What is Sabril, and how does it work?

Sabril is a prescription medicine used along with other
treatments to treat adults and children 10 years and older with complex partial
seizures (CPS) if:

The CPS does not respond well enough to several other
treatments, and
You and your healthcare provider decide the possible
benefit of taking Sabril is more important than the risk of vision loss.

Sabril should not be the first medicine used to treat CPS.

Sabril is also used to treat babies 1 month to 2 years of
age who have infantile spasms (IS) if you and your healthcare provider decide
the possible benefits of taking Sabril are more important than the possible
risk of vision loss.

What are the side effects of Sabril?

WARNING

PERMANENT VISION LOSS

Sabril can cause permanent bilateral concentric visual field constriction,
including tunnel vision that can result in disability. In some cases, Sabril
also can damage the central retina and may decrease visual acuity.
The onset of vision loss
from Sabril is unpredictable, and can occur within weeks of starting treatment
or sooner, or at any time after starting treatment, even after months or years.
Symptoms of vision loss from
Sabril are unlikely to be recognized by patients or caregivers before vision
loss is severe. Vision loss of milder severity, while often unrecognized by the
patient or caregiver, can still adversely affect function.
The risk of vision loss
increases with increasing dose and cumulative exposure, but there is no dose or
exposure known to be free of risk of vision loss.
Vision assessment is recommended at baseline (no later
than 4 weeks after starting Sabril), at least every 3 months during therapy,
and about 3 to 6 months after the discontinuation of therapy.
Once detected, vision loss due to Sabril is not
reversible. It is expected that, even with frequent monitoring, some patients
will develop severe vision loss.
Consider drug
discontinuation, balancing benefit and risk, if vision loss is documented.
Risk of new or worsening
vision loss continues as long as Sabril is used. It is possible that vision
loss can worsen despite discontinuation of Sabril.
Because of the risk of
vision loss, Sabril should be withdrawn from patients with refractory complex
partial seizures who fail to show substantial clinical benefit within 3 months
of initiation and within 2-4 weeks of initiation for patients with infantile
spasms, or sooner if treatment failure becomes obvious. Patient response to and
continued need for Sabril should be periodically reassessed.
Sabril should not be used in
patients with, or at high risk of, other types of irreversible vision loss
unless the benefits o f treatment clearly outweigh the risks.
Sabril should not be used with other drugs associated
with serious adverse ophthalmic effects such as retinopathy or glaucoma unless
the benefits clearly outweigh the risks.
Use the lowest dosage and shortest exposure to Sabril consistent with
clinical objectives.

Because of the risk of permanent vision loss, Sabril is available only
through a restricted program under a Risk Evaluation and Mitigation Strategy
(REMS) called the Vigabatrin REMS Program. Further information is available
at www.vigabatrinREMS.com or 1-866-244-8175.

Sabril can cause serious side effects, including:

Permanent vision loss
Magnetic resonance imaging (MRI) changes in babies
with infantile spasms (IS)
Risk of suicidal thoughts or actions

1. Permanent vision loss:

Sabril can damage the vision of anyone who takes it.
People who take Sabril do not lose all of their vision, but some people can
have severe loss particularly to their ability to see to the side when they
look straight ahead (peripheral vision). With severe vision loss, you may only
be able to see things straight in front of you (sometimes called “tunnel vision”).
You may also have blurry vision. If this happens, it will not get better.

Vision loss and use of Sabril in adults and children
10 years and older: Because of the risk of vision loss, Sabril is used to
treat complex partial seizures (CPS) only in people who do not respond well
enough to several other medicines.

Tell your healthcare provider right away if you (or
your child):

might not be seeing as well as before starting Sabril
start to trip, bump into things, or are more clumsy than
usual
are surprised by people or things coming in front of you
that seem to come out of nowhere

These changes can mean that you (or your child) have
damage to your vision.
It is recommended that your healthcare provider test your
(or your child’s) vision (including peripheral vision) andvisual acuity
(ability to read an eye chart) before you (or your child) start Sabril or
within 4 weeks after starting Sabril, and at least every 3 months after that
until Sabril is stopped. It is also recommended that you (or your child) have a
vision test about 3 to 6 months after Sabril is stopped.
Some people are not able to complete testing of
vision.Your healthcare provider will determine if you (or your child) can be
tested. If you (or your child) cannot complete vision testing, your healthcare
provider may continue prescribing Sabril, but your healthcare provider will not
be able to watch for any vision loss you (or your child) may get.
Even if your vision (or your child’s vision) seems fine,
it is important that you get these regular vision tests because vision damage
can happen before you (or your child) notice any changes.
These vision tests cannot prevent the vision damage that
can happen with Sabril, but they do allow the healthcare provider to decide if
you (or your child) should stop Sabril if vision has gotten worse, which
usually will lessen further damage.
If you do not have these vision tests regularly, your
healthcare provider may stop prescribing Sabril.
If you drive and your vision is damaged by Sabril,
driving might be more dangerous, or you may not be able to drive safely at all.
Talk about this with your healthcare provider.
Vision loss in babies: Because of the risk of
vision loss, Sabril is used in babies 1 month to 2 years of age with infantile
spasms (IS) only when you and your healthcare provider decide that the possible
benefits of Sabril are more important than the risks.
- Parents or caregivers are not likely to recognize the
  symptoms of vision loss in babies until it is severe. Healthcare providers may
  not find vision loss in babies until it is severe.
- It is difficult to test vision in babies, but, to the
  extent possible, all babies should have their vision tested before starting
  Sabril or within 4 weeks after starting Sabril, and every 3 months after that
  until Sabril is stopped.Your baby should also have a vision test about 3 to 6
  months after Sabril is stopped.
- Your baby may not be able to be tested. Your healthcare
  provider will determine if your baby can be tested. If your baby cannot be
  tested, your healthcare provider may continue prescribing Sabril, but your
  healthcare provider will not be able to watch for any vision loss.

Tell your healthcare provider right away if you think
that your baby is:

not seeing as well as before taking Sabril
acting differently than normal

Even if your baby’s vision seems fine, it is important to
get regular vision tests because damage can happen before your baby acts
differently. Even these regular vision exams may not show the damage to your
baby’s vision before it is serious and permanent.

All people who take Sabril:

You are at risk for permanent vision loss with any amount
of Sabril.
Your risk of vision loss may be higher the more Sabril you take daily and the longer you take it.
It is not possible for your healthcare provider to know
when vision loss will happen. It could happen soon after starting Sabril or any
time during treatment. It may even happen after treatment has stopped.

Because Sabril might cause permanent vision loss, it is
available to healthcare providers and patients only under a special program
called the Vigabatrin Risk Evaluation and Mitigation Strategy (REMS) Program.
Sabril can only be prescribed to people who are enrolled in this program . As
part of the Vigabatrin REMS Program, it is recommended that your healthcare
provider test your (or your child’s) vision from time to time (periodically)
while you (or your child) are being treated with Sabril, and even after you (or
your child) stop treatment. Your healthcare provider will explain the details
of the Vigabatrin REMS Program to you. For more information, go to
www.vigabatrinREMS.com or call 1-866-244-8175.

2. Magnetic resonance imaging (MRI) changes in babies
with infantile spasms:

Brain pictures taken by magnetic resonance imaging (MRI)
show changes in some babies after they are given Sabril. It is not known if
these changes are harmful.

3. Risk of suicidal thoughts or actions:

Like other antiepileptic drugs, Sabril may cause suicidal
thoughts or actions in a very small number of people, about 1 in 500 people
taking it. Call a healthcare provider right away if you or your child have any
of these symptoms, especially if they are new, worse, or worry you:

thoughts about suicide or dying
attempts to commit suicide
new or worse depression
new or worse anxiety
feeling agitated or restless
panic attacks
trouble sleeping (insomnia)
new or worse irritability
acting aggressive, being angry, or violent
acting on dangerous impulses
an extreme increase in activity and talking (mania)
other unusual changes in behavior or mood

Suicidal thoughts or actions can be caused by things
other than medicines. If you or your child have suicidal thoughts or actions,
your healthcare provider may check for other causes.

What are the possible side effects of Sabril?

Sabril can cause serious side effects, including:

sleepiness and tiredness.
Sabril may cause your baby to be sleepy. Sleepy
babies may have a harder time suckling and feeding, or may be irritable.
weight gain that happens without swelling

The following serious side effects happen in adults. It
is not known if these side effects also happen in babies who take Sabril.

low red blood cell counts (anemia)
nerve problems. Symptoms of a nerve problem can
include numbness and tingling in your toes or feet. It is not known if nerve
problems will go away after you stop taking Sabril.
swelling

If you or your child has CPS, Sabril may make certain
types of seizures worse. Tell your healthcare provider right away if your (or
your child’s) seizures get worse.

The most common side effects of Sabril in adults include:

problems walking or feeling uncoordinated
feeling dizzy
shaking (tremor)
joint pain
memory problems and not thinking clearly
eye problems: blurry vision, double vision and eye
movements that you cannot control

The most common side effects of Sabril in children 10
to 16 years of age include:

Also expect side effects like those seen in adults

If you are giving Sabril to your baby for IS:

Sabril may make certain types of seizures worse. You
should tell your baby’s healthcare provider right away if your baby’s seizures
get worse. Tell your baby’s healthcare provider if you see any changes in your
baby’s behavior.

The most common side effects of Sabril in babies include:

sleepiness -Sabril may cause your baby to be sleepy.
Sleepy babies may have a harder time suckling and feeding, or may be irritable.
swelling in the bronchial tubes (bronchitis)
ear infection
irritability

Tell your healthcare provider if you or your child have
any side effect that bothers you or that does not go away. These are not all
the possible side effects of Sabril.

Call your doctor for medical advice about side effects.
You may report side effects to FDA at 1-800-FDA-1088.

Does Sabril cause addiction or withdrawal symptoms?

Drug Abuse And Dependence

Controlled Substance

Vigabatrin is not a controlled substance.

Abuse

Vigabatrin did not produce adverse events or overt behaviors associated with abuse when administered to humans or animals.
It is not
possible to predict the extent to which a CNS active drug will be misused, diverted, and/or abused once marketed.
Consequently,
physicians should carefully evaluate patients for history of drug abuse and follow such patients closely, observing them for signs of
misuse or abuse of vigabatrin (e.g., incrementation of dose, drug-seeking behavior).

Dependence

Following chronic administration of vigabatrin to animals, there were no
apparent withdrawal signs upon drug discontinuation.
However, as with all AEDs,
vigabatrin should be withdrawn gradually to minimize increased seizure
frequency.

What is the dosage for Sabril?

Important Dosing And Administration Instructions

Dosing

Use the lowest dosage and shortest exposure to Sabril consistent with
clinical objectives.
The Sabril dosing regimen depends on the indication, age group, weight, and
dosage form (tablets or powder for oral solution). Patients with impaired renal
function require dose adjustment.
Sabril tablets and powder for oral solution are bioequivalent. Either tablet or powder can be used for CPS. Powder for oral solution
should be used for IS; tablets should not be used for IS because of difficulty in the administration of tablets to infants and young
children.
Monitoring of Sabril plasma concentrations to optimize therapy is not helpful.

Administration

Sabril is given orally with or without food.
Sabril powder for oral solution should be mixed with water prior to
administration.
If a decision is made to discontinue Sabril, the dose should be gradually
reduced.

Refractory Complex Partial Seizures

Adults (Patients 17 Years Of Age And Older)

Treatment should be initiated at 1000 mg/day (500 mg twice daily).
Total daily dose may be increased in 500 mg increments at
weekly intervals, depending on response.
The recommended dose of Sabril in adults is 3000 mg/day (1500 mg twice daily).
A
6000 mg/day dose has not been shown to confer additional benefit compared to the 3000 mg/day dose and is associated with an
increased incidence of adverse events.
In controlled clinical studies in adults with complex partial seizures,
Sabril was tapered by decreasing the daily dose 1000 mg/day on a weekly basis
until discontinued.

Pediatric (Patients 10 To 16 Years Of Age)

Treatment is based on body weight as shown in Table 1.
Treatment should be initiated at a total daily dose of 500 mg/day (250 mg
twice daily) and may be increased weekly in 500 mg/day increments to a total maintenance dose of 2000 mg/day (1000 mg twice
daily).
Patients weighing more than 60 kg should be dosed according to adult recommendations.

Table 1. Pediatric CPS Dosing Recommendations

Body Weight
[kg]
Total Daily*
Starting Dose
[mg/day]
Total Daily*
Maintenance Dose^†
[mg/day]

25 to 60^††
500
2000

*Administered in two divided doses.
^†Maintenance dose is based on 3000 mg/day adult-equivalent dose
^†† Patients weighing more than 60 kg should be dosed according to adult recommendations

In patients with refractory complex partial seizures, Sabril should be
withdrawn if a substantial clinical benefit is not observed within 3 months of
initiating treatment.
If, in the clinical judgment of the prescriber, evidence
of treatment failure becomes obvious earlier than 3 months, treatment should be
discontinued at that time.
In a controlled study in pediatric patients with complex partial seizures,
Sabril was tapered by decreasing the daily dose by one third every week for
three weeks.

Infantile Spasms

The initial daily dosing is 50 mg/kg/day given in two divided doses (25 mg/kg
twice daily); subsequent dosing can be titrated by 25 mg/kg/day to 50 mg/kg/day
increments every 3 days, up to a maximum of 150 mg/kg/day given in 2 divided
doses (75 mg/kg twice daily).
Table 2 provides the volume of the 50 mg/mL dosing solution that should be administered as individual doses in infants of various
weights.

Table 2. Infant Dosing Table

Weight
[kg]
Starting Dose
50 mg/kg/day
Maximum Dose
150 mg/kg/day

3
1.5 mL twice daily
4.5 mL twice daily

4
2 mL twice daily
6 mL twice daily

5
2.5 mL twice daily
7.5 mL twice daily

6
3 mL twice daily
9 mL twice daily

7
3.5 mL twice daily
10.5 mL twice daily

8
4 mL twice daily
12 mL twice daily

9
4.5 mL twice daily
13.5 mL twice daily

10
5 mL twice daily
15 mL twice daily

11
5.5 mL twice daily
16.5 mL twice daily

12
6 mL twice daily
18 mL twice daily

13
6.5 mL twice daily
19.5 mL twice daily

14
7 mL twice daily
21 mL twice daily

15
7.5 mL twice daily
22.5 mL twice daily

16
8 mL twice daily
24 mL twice daily

In patients with infantile spasms, Sabril should be withdrawn if a
substantial clinical benefit is not observed within 2 to 4 weeks. If, in the
clinical judgment of the prescriber, evidence of treatment failure becomes
obvious earlier than 2 to 4 weeks, treatment should be discontinued at that
time.

In a controlled clinical study in patients with infantile spasms, Sabril was tapered by decreasing the daily dose at a rate of 25 mg/kg
to 50 mg/kg every 3 to 4 days

Patients With Renal Impairment

Sabril is primarily eliminated through the kidney.

Infants

Information about how to adjust the dose in infants with renal impairment is unavailable.

Adult And Pediatric Patients 10 Years And Older

Mild renal impairment (CLcr >50 to 80 mL/min): dose should be decreased by 25%
Moderate renal impairment (CLcr >30 to 50 mL/min): dose should be decreased by 50%
Severe renal impairment (CLcr >10 to 30 mL/min): dose should be decreased by 75%

CLcr in mL/min may be estimated from serum creatinine (mg/dL) using the following formulas:

Patients 10 to <12 years old: CLcr (mL/min/1.73 m²) = (K × Ht) / Scr
- height (Ht) in cm; serum creatinine (Scr) in mg/dL
  - K (proportionality constant): Female Child (<12 years): K=0.55;
  - Male Child (<12 years): K=0.70
Adult and pediatric patients 12 years or older: CLcr (mL/min) = [140-age (years)] × weight (kg) / [72 × serum creatinine (mg/dL)] (×0.85 for female patients)

The effect of dialysis on Sabril clearance has not been adequately studied.

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What drugs interact with Sabril?

Antiepileptic Drugs

Phenytoin

Although phenytoin dose adjustments are not routinely required, dose
adjustment of phenytoin should be considered if clinically indicated, since
Sabril may cause a moderate reduction in total phenytoin plasma levels.

Clonazepam

Sabril may moderately increase the Cmax of clonazepam resulting in an
increase of clonazepam-associated adverse reactions.

Other AEDs

There are no clinically significant pharmacokinetic interactions between
Sabril and either phenobarbital or sodium valproate.
Based on population
pharmacokinetics, carbamazepine, clorazepate, primidone, and sodium valproate
appear to have no effect on plasma concentrations of vigabatrin.

Oral Contraceptives

Sabril is unlikely to affect the efficacy of steroid oral contraceptives.

Drug-Laboratory Test Interactions

Sabril decreases alanine transaminase (ALT) and aspartate transaminase (AST) plasma activity in up to 90% of patients. In some
patients, these enzymes become undetectable.
The suppression of ALT and AST activity by Sabril may preclude the use of these
markers, especially ALT, to detect early hepatic injury.
Sabril may increase the amount of amino acids in the urine, possibly leading to a false positive test for certain rare genetic
metabolic diseases (e.g., alpha aminoadipic aciduria).

Is Sabril safe to use while pregnant or breastfeeding?

There are no adequate and well-controlled studies in pregnant women.
Sabril should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.
Pregnant patients taking Sabril should enroll in the North American Antiepileptic Drug (NAAED) Pregnancy Registry.
This can be done by calling the toll free number 1-888-233-2334, and must be done by patients themselves.
Information on the registry can also be found at the website http://www.aedpregnancyregistry.org/.
Vigabatrin is excreted in human milk.
Because of the potential for serious adverse reactions from vigabatrin in nursing infants, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.

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