A 22-year-old male is brought to the emergency department with sudden onset of involuntary muscle spasms, including torticollis and oculogyric crisis, occurring shortly after receiving his first dose of haloperidol for acute psychosis. Which of the following is the most appropriate immediate treatment?

Explanation

The patient is experiencing acute dystonia, a type of extrapyramidal symptom (EPS) that can occur rapidly after initiating typical antipsychotics like haloperidol. Acute dystonia is characterized by sudden, sustained muscle contractions. The most effective immediate treatment involves anticholinergic medications, such as benztropine, or antihistamines with anticholinergic properties, such as diphenhydramine (intramuscular or intravenous). Lorazepam (A) might help with anxiety but is not the primary treatment for dystonia. Intravenous haloperidol (C) would worsen the condition. Propranolol (D) is used for akathisia, not acute dystonia.