A 68-year-old man with schizophrenia treated with haloperidol for several years develops repetitive orofacial movements with lip smacking and tongue protrusion that persist even after the dose is reduced. The psychiatrist decides to treat the tardive dyskinesia pharmacologically. The drug chosen works by which mechanism?
- A Inhibits the vesicular monoamine transporter 2 (VMAT2), reducing presynaptic dopamine release ✓
- B Stimulates dopamine D2 receptors to compensate for antipsychotic-induced blockade
- C Blocks muscarinic receptors in the nigrostriatal pathway
- D Enhances GABAergic transmission by increasing chloride channel opening
Correct answer: A. Inhibits the vesicular monoamine transporter 2 (VMAT2), reducing presynaptic dopamine release
Explanation
Tardive dyskinesia is managed with VMAT2 inhibitors such as valbenazine and deutetrabenazine, which block packaging of dopamine into synaptic vesicles and thereby reduce dopamine release into the synapse. Giving a dopamine agonist would worsen psychosis and is not a treatment. Anticholinergics treat drug-induced parkinsonism and acute dystonia but tend to aggravate tardive dyskinesia. Benzodiazepines have no established role in reversing the involuntary movements.
Reference: Katzung Basic and Clinical Pharmacology, 16th ed.
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Written and medically reviewed by the StethoPrep medical team.