A 40-year-old woman taking metoclopramide for gastroparesis develops acute torticollis and oculogyric crisis one hour after the dose. The emergency physician administers a drug that reverses these symptoms within minutes. Which drug was most likely administered?
- A Diazepam
- B Procyclidine (or benztropine) ✓
- C Promethazine
- D Haloperidol
Correct answer: B. Procyclidine (or benztropine)
Explanation
The described symptoms constitute an acute dystonic reaction caused by dopamine D2 receptor blockade by metoclopramide in the basal ganglia. Anticholinergic drugs such as procyclidine, benztropine, or diphenhydramine rapidly reverse acute dystonia by restoring the dopaminergic-cholinergic balance in the striatum. Diazepam may provide partial relief via muscle relaxation but does not target the mechanism. Haloperidol would worsen dopamine blockade.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
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