An infantile spasm syndrome refractory to standard therapy is treated with an antiepileptic that acts by irreversible inhibition of GABA-transaminase, thereby raising brain GABA concentrations. A mandatory baseline investigation before starting this drug is:

• A Visual field testing ✓
• B Audiometry
• C Nerve conduction study
• D Echocardiography

Explanation

The drug described is vigabatrin, an irreversible inhibitor of GABA-transaminase (GABA-T). Its most feared adverse effect is concentric constriction of the visual field, which is often asymptomatic and may be irreversible, so baseline and periodic visual field assessment (or VEP-based screening in infants) is required before and during therapy. Audiometry, nerve conduction studies and echocardiography are not associated with vigabatrin toxicity.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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