Dystonic Reaction

Neuroleptic agents, antiemetics (e.g., prochlorperazine [Compazine] or metoclopramide [Reglan]), and occasionally other agents can cause extrapyramidal side effects. Dystonia, akathisia, and akinesis may occur with phenothiazine use and are generally responsive to treatment; tardive dyskinesia occurs after longer-term neuroleptic therapy and is usually not reversible. Patients with dystonia are most likely to seek treatment in the ED because symptoms are acute in onset and severe. Dystonia may develop hours or days after drug exposure.

The diagnosis of dystonia should be entertained in patients currently taking a suspected medication (or those who have recently taken a single dose) and report a characteristic onset of muscle spasms of the neck or face. Patients should be specifically questioned about exposure to drugs that commonly cause dystonia. The presentation is often dramatic and, when suspected, is easily treated.

Causes

• Neuroleptics, antiemetics, and antidepressants are the most common causes of drug-induced dystonic reactions.
• Acute dystonic reactions have been described with every antipsychotic.
• Alcohol and cocaine use increase risk.
• Family history of dystonia
• Viral infections

These are the most common causes of Predisposing factors and Drug-related adverse effects.

Symptoms

• Severe neck discomfort and stiffness
• Difficulty with speech

Signs

• Acute torticollis
• Elevation of the shoulder
• Upward deviation of the eyes (oculogyric crisis)
• Protrusion of tongue
• Arching of back (opisthotonos)

Treatment

Dystonia responds promptly to the anticholinergic benztropine 1-2 mg by slow intravenous injection. Most patients respond within 5 minutes and are symptom-free by 15 minutes.

Promethazine, 25-50 mg intravenously or intramuscularly, has been used less frequently but it works and it is readily available in most emergency departments. It may be a useful alternative for the uncommon patient who has both dystonia and significant anticholinergic symptoms from antipsychotic drugs.

Diazepam, 5-10 mg intravenously, has been used for the rare patient who does not completely respond to the more specific antidotes. Unlike the other antidotes, it cannot be given intramuscularly.

There are rare case reports of dystonia caused by all of these treatments, including diazepam.

Children should be given parenteral benztropine, 0.02 mg/kg to a maximum of 1 mg, either intramuscularly. This can be repeated once, but if the intramuscular route is chosen, allow 30 minutes to elapse before repeating. The same dose should be given orally, twice daily for the next 24-48 hours to prevent recurrence. Benztropine comes in a 2 mg tablet, so the dose needs to be approximated to the nearest 0.5 mg.