Situation: A 22-year-old man with a first episode of psychosis is admitted to an acute psychiatric unit. He receives haloperidol 5 mg intramuscularly (IM) for severe agitation and is then started on oral haloperidol. Six hours after the injection, his neck twists to one side, his eyes roll upward, and he is frightened. He is breathing without difficulty. Which as-needed (PRN) order should the nurse carry out?

Torticollis and oculogyric crisis within hours of a high-potency first-generation antipsychotic are acute dystonia. Treatment is an anticholinergic, benztropine or diphenhydramine, given intramuscularly or intravenously for rapid effect, while the nurse stays with the client and watches the airway for laryngospasm.

Recognizing the emergency
The neck twisting to one side is torticollis, and the upward deviation of the eyes is oculogyric crisis. Together they form the classic picture of acute dystonia, a distressing extrapyramidal reaction that can appear within hours after a high-potency first-generation antipsychotic such as haloperidol ^[2]. The patient is frightened but breathing without difficulty, so the immediate priority is to reverse the sustained muscle contraction before it progresses or recurs.

Why this is acute dystonia
Acute dystonia is a drug-induced movement disorder caused by dopamine receptor blockade, especially with potent D2 antagonists ^[1][3]. Haloperidol is one of the highest-potency agents, and the intramuscular route produces a rapid rise in drug levels, which explains why symptoms emerged only 6 hours after the injection ^[2]. Younger age and male sex are additional risk factors, and this patient is a 22-year-old man, placing him in a higher-risk group ^[2]. The sustained contraction of neck and extraocular muscles reflects the same mechanism that can, in rare cases, involve the laryngeal muscles and threaten the airway ^[4].

Why an anticholinergic is the treatment
Acute dystonia responds rapidly to drugs that restore the balance between dopamine and acetylcholine in the basal ganglia. The definitive treatment is an anticholinergic agent such as benztropine or diphenhydramine, given intramuscularly or intravenously for rapid onset. ^[1] In this scenario, diphenhydramine 50 mg IM is the correct PRN order because the intramuscular route acts faster than the oral route and avoids the delay of swallowing a tablet during an active dystonic episode.

Watch out! Benztropine 2 mg by mouth is also an anticholinergic, but the oral route is slower and less reliable when the patient is frightened and actively dystonic. The question asks which PRN order to carry out now, so the intramuscular option is preferred.

Why the other options are incorrect
Lorazepam 2 mg IM may reduce anxiety and muscle spasm, but it is not the first-line antidote for acute dystonia. It does not directly correct the dopaminergic-cholinergic imbalance. Haloperidol 5 mg IM would worsen the dystonia because it adds more dopamine blockade to the same system that caused the reaction ^[2][3]. Giving more haloperidol is contraindicated.

Option	Drug class	Effect on acute dystonia	Appropriate now?
Diphenhydramine 50 mg IM	Anticholinergic	Reverses dystonia rapidly	Yes — correct choice
Benztropine 2 mg PO	Anticholinergic	Reverses dystonia, but slower oral onset	Less ideal for immediate relief
Lorazepam 2 mg IM	Benzodiazepine	Sedation and muscle relaxation only	Not first-line antidote
Haloperidol 5 mg IM	High-potency antipsychotic	Worsens dopamine blockade	Contraindicated

Airway vigilance after treatment
Although this patient is breathing without difficulty, acute dystonia can involve the laryngeal muscles. Acute laryngeal dystonia is a rare but potentially fatal complication of haloperidol that can narrow the airway and progress to respiratory failure if not recognized early. ^[4] After giving diphenhydramine, the nurse should remain with the patient, monitor for stridor, hoarseness, or respiratory distress, and ensure emergency airway equipment is available ^[4]. The anticholinergic usually relieves the torticollis and oculogyric crisis within minutes, but observation must continue because dystonia can recur as the anticholinergic wears off.

Key point! The combination of neck twisting and upward eye deviation hours after haloperidol is acute dystonia, and the correct immediate intervention is an intramuscular anticholinergic — diphenhydramine — not more haloperidol. ^[1][2]