An elderly man with schizophrenia on haloperidol for years develops orofacial choreiform movements diagnosed as tardive dyskinesia. Which agent, approved specifically for this condition, works by a mechanism unlike any other psychotropic?

• A Valbenazine, a reversible VMAT2 inhibitor ✓
• B Amantadine, an NMDA antagonist
• C Clonazepam, a long-acting benzodiazepine
• D Propranolol, a beta blocker acting centrally

Explanation

Tardive dyskinesia reflects dopaminergic supersensitivity after chronic D2 blockade. Depletion of presynaptic dopamine stores improves it. Valbenazine and deutetrabenazine are reversible inhibitors of vesicular monoamine transporter 2 (VMAT2), blocking packaging of dopamine into synaptic vesicles and thereby reducing dopamine release. Reserpine acts similarly by irreversible VMAT2 blockade. Amantadine, clonazepam and propranolol are older off-label options with weaker evidence and different mechanisms.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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