Which antiepileptic acts as an irreversible inhibitor of GABA transaminase, thereby raising brain GABA levels, but is restricted in adult use because it causes concentric visual field constriction?

• A Tiagabine
• B Retigabine
• C Zonisamide
• D Vigabatrin ✓

Explanation

Vigabatrin irreversibly inhibits GABA transaminase, increasing CNS GABA. It is used for infantile spasms (West syndrome) and refractory focal seizures, but progressive bilateral visual field loss limits its use. Tiagabine blocks the GAT-1 reuptake transporter rather than the degrading enzyme, and does not cause field defects. Zonisamide acts on sodium channels and calcium currents, and retigabine opens KCNQ potassium channels.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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