Vigabatrin side effects

Short answer: in babies, the most common side effects of vigabatrin are sleepiness and irritability, and some babies show changes on brain MRI scans that usually go away when the medicine is stopped. In older children and adults, drowsiness, dizziness, fatigue and weight gain are common, and mood changes such as depression are reported more often than with placebo.^1,2,3 The most serious risk at every age is permanent loss of side vision, which is why vigabatrin carries a boxed warning.²

Sabril, Vigafyde, Vigadrone and other generic versions all contain the same medicine. Vigadrone is a generic powder approved through an abbreviated application, so what this page says applies to it too.^4,5

• Vigabatrin
• Comparison group

Brain MRI changes in infants with spasms

Vigabatrin

22%

Other treatments

4%

Weight gain of 7% or more (pooled pediatric trials)

Vigabatrin

47%

Placebo

19%

Show as a table

Group	Measure	Value
Brain MRI changes in infants with spasms	Vigabatrin	22%
Brain MRI changes in infants with spasms	Other treatments	4%
Weight gain of 7% or more (pooled pediatric trials)	Vigabatrin	47%
Weight gain of 7% or more (pooled pediatric trials)	Placebo	19%

Side effects in babies

A review of non-vision side effects found that sedation, sleepiness and irritability are the side effects seen most often in infants.¹ A sleepier baby may feed less well. If that happens, talk to the prescriber before changing anything. Some families find it helps to plan feeds and quiet time around doses, but the prescriber should decide whether the dose or timing needs to change.

Changes on brain MRI scans

Some babies on vigabatrin show new signal changes on brain MRI scans. Many of these babies have no symptoms from them, but some do.^7,8

• How common. In a study of 205 babies with infantile spasms, MRI changes were seen in 22% of those on vigabatrin and 4% of those on other treatments. The FDA labels quote these figures.^2,6 The same study found no extra MRI changes in children or adults treated for refractory complex partial seizures.⁶
• Who is affected. In other studies, affected babies tended to be younger, often under 12 months, and on higher doses.^9,10
• Do they go away? In the studies that followed babies up, the changes usually went away after vigabatrin was stopped. In the 205-baby study they cleared in 6 of the 9 babies with a follow-up scan.^6,9,10

What affects the risk is debated. One study linked the symptom-free MRI changes to the highest daily dose a baby reached, and its authors advised caution above 175 mg/kg/day. That study also found a small number of babies with symptoms from the changes, possibly linked to taking hormone treatment at the same time.⁷ A 2025 study found that babies with symptoms were more likely to be on hormone treatment as well, but did not find a link with peak dose.⁸ If your baby is on both vigabatrin and a hormone treatment such as steroids or ACTH, ask the neurologist how they plan to watch for this.

The same review of non-vision side effects also discusses the history of intramyelinic edema, a type of swelling within the brain's white matter.¹

Side effects in children and adults

Drowsiness, dizziness and fatigue

In adults, the most common side effects are drowsiness, dizziness, headache and fatigue.¹ A Cochrane review of 11 add-on trials found that people on vigabatrin had more dizziness, fatigue and drowsiness than people on placebo, and were nearly three times as likely to stop treatment early.³ In pooled pediatric trials, sleepiness was reported in 6% on vigabatrin vs 5% on placebo, and fatigue in 10% vs 7%.²

Weight gain

Weight gain is one of the clearer differences from placebo. In pooled pediatric trials, 47% of children on vigabatrin gained 7% or more of their body weight, against 19% on placebo.² In a trial in people with newly diagnosed epilepsy, weight gain was reported in 11% on vigabatrin and 5% on carbamazepine.¹¹

Mood and behavior

Depression was reported more often with vigabatrin than with placebo in the Cochrane review, and psychosis has also been reported more often than with placebo.^1,3 In the trial against carbamazepine, psychiatric symptoms were reported in 25% on vigabatrin vs 15% on carbamazepine.¹¹ Tell the prescriber about new or worsening low mood, agitation or unusual behavior. If someone talks about harming themselves, call or text 988 in the US, or call emergency services.

The Cochrane results come from people aged 10 to 64, and the authors say they should not be applied to children under 10.³

Vision loss

Vigabatrin can cause permanent loss of side vision in both eyes, and it can also reduce sharpness of vision. The risk rises with dose and with total time on the medicine, and no dose is known to be free of risk.² Based on adult studies, the label says 30% or more of patients can be affected.¹² Everyone on vigabatrin has regular vision checks through the REMS program. See vision loss for how common it is, how it is tested in babies and what to watch for.

Stopping vigabatrin suddenly

Do not stop vigabatrin suddenly. Stopping all at once can bring on seizures, so the dose is lowered step by step. In the infantile spasms study, the dose was lowered by 25 to 50 mg/kg every 3 to 4 days.² The prescriber sets the plan. See dosage for more.

Too much vigabatrin

If you think your child or anyone else has taken too much vigabatrin, call Poison Help at 1-800-222-1222 in the US. Call emergency services if the person is very hard to wake, has trouble breathing or has a seizure. Keep the bottle or packet with you when you call.

The simplest protection against dosing mistakes is a clear routine: use the oral syringe from the pharmacy and get the dose in mL in writing.² When babies switch between forms, the volume changes even though the dose in mg does not. See liquid vs powder.

When to call the prescriber

• Your baby is too sleepy to feed well, or is much more irritable than usual.
• Your child seems to bump into things, misses objects at the side, or does not follow faces or toys as before.
• You notice low mood, agitation or other behavior changes.
• Seizures or spasms come back or get worse.
• You have missed doses or think a dose was wrong.