An antiepileptic acts by irreversible inhibition of GABA transaminase, thereby raising brain GABA concentrations. Long-term therapy with this drug mandates periodic ophthalmological assessment because of which adverse effect?

• A Retinal pigmentary degeneration
• B Optic disc oedema with papilloedema
• C Cataract formation
• D Concentric constriction of the visual field ✓

Explanation

Vigabatrin irreversibly inhibits GABA-transaminase (GABA-T), increasing CNS GABA. Its major limiting toxicity is an insidious, often asymptomatic concentric visual field constriction that may be irreversible, so formal perimetry is advised before and during therapy. It is used mainly for infantile spasms and refractory focal seizures when benefits outweigh this risk. Retinal degeneration is associated with chloroquine type agents, not vigabatrin.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.