Vigabatrin !

An irreversible inhibitor of the enzyme that breaks down GABA, used for infantile spasms and refractory focal seizures. It can cause permanent vision loss.

Updated 2026-11-01

Class: Antiseizure medicines
Enzyme: GABA transaminase (GABA-T)
ATC code: N03AG04

GABA transaminase (GABA-T)Vigabatrin

The figure shows the pig enzyme GABA aminotransferase inactivated by vigabatrin, which stays covalently attached in the active site (ligand VIG); the human enzyme is closely related.

Target in 3D: GABA transaminase (GABA-T). PDB structure 1OHW (RCSB PDB, public domain). View the structure at RCSB PDB

Mechanism of action

Vigabatrin is a GABA analogue that irreversibly inhibits GABA transaminase, the enzyme that breaks GABA down. GABA builds up in the brain, strengthening inhibition. Because the enzyme is destroyed, the effect lasts until new enzyme is made.

Enters the active site of GABA transaminase
Binds it irreversibly (suicide inhibition)
GABA is not broken down and builds up
Stronger inhibition reduces seizures and spasms

Pharmacokinetics

Absorption: Absorbed by mouth; food slows absorption without changing the total amount
Elimination: Mainly by the kidneys; the dose is adjusted in kidney disease

Indications

Infantile spasms in infants and young children Epilepsy and seizures →
Refractory focal (complex partial) seizures as add-on treatment Epilepsy and seizures →

Adverse effects

Common

Sleepiness and fatigue
Blurred vision
Dizziness, poor coordination and tremor
Weight gain
Headache

Contraindications

None listed in the label; the risk of vision loss limits its use to cases where the benefit is clear

Key interactions

Phenytoin: Lower phenytoin levels
Other drugs with serious eye effects (retinopathy, glaucoma): Avoided together unless the benefit clearly outweighs the risk

What is monitored

Vision testing at baseline and regularly during treatment and after it stops
Early review of benefit: stopped if there is no clear response
Signs of anaemia
MRI changes in infants when imaging is done

Administration and safety

Given by mouth as tablets or powder for oral solution
In some countries available only through a restricted programme because of the vision risk
Withdrawn gradually

Nursing care

Explain that vision loss may not be noticed until it is severe, so eye tests are essential
Check that vision assessments happen on schedule
In infants, watch alertness and feeding
Teach to report bumping into objects or clumsiness that may reflect narrowed vision

Pregnancy and breastfeeding

Human data are limited; it passes into breast milk. Benefits and risks are weighed with specialist care.

Test yourself

Think of the answer, then tap the question to see it.

What enzyme does vigabatrin inhibit, and how?

GABA transaminase, irreversibly; GABA is no longer broken down and builds up in the brain.

What is the boxed warning of vigabatrin?

Permanent bilateral concentric visual field loss (tunnel vision), which may go unnoticed until it is severe.

In which childhood epilepsy is vigabatrin a key treatment?

Infantile spasms.

Add to my cards (3)

Tiagabine

Epilepsy and seizures

← Back to the class: Antiseizure medicines

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: Vigabatrin: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2025); DailyMed - VIGABATRIN tablet (DailyMed (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Representative model, for educational purposes only.