Case Presentation: A 25-year-old male with polysubstance abuse presented with 5-days of sweats, chills, confusion, nausea, vomiting, dehydration, and anorexia in the setting of opioid detoxification. On presentation, he was afebrile, tachycardic to 115 bpm, with otherwise normal vitals. Exam revealed a tired-appearing thin man. Labs were consistent with mild dehydration. His urine toxicology screen was positive for cannabinoids and fentanyl. He was admitted to the hospital for symptomatic management of opioid withdrawal. He continued to have nausea and received intravenous prochlorperazine. Later that evening, he experienced two 30-60 second acute episodes of intermittent back/neck arching and facial contorting. During the episodes, he was able to answer questions appropriately and follow commands; his heart rate was also noted to have increased to 160 bpm. He had no increased tone, clonus, or hyperreflexia. He received lorazepam 0.5 mg IV without further events following administration. Subsequently, his neurologic exam was normal and his tachycardia improved. He was placed on continuous video electroencephalogram (vEEG) monitoring. He later received another dose of prochlorperazine and shortly thereafter experienced another similar event caught on vEEG (image 1); no epileptiform activity was demonstrated.He was diagnosed with an acute dystonic reaction secondary to prochlorperazine, which was discontinued. He was started on clonazepam 0.5 mg PO TID and had no further events. Within 48 hours, he safely discharged with substance abuse resources.
Discussion: Acute dystonic reaction is a movement disorder that may occur secondary to certain medications including antipsychotics, antiemetics, and anticonvulsants.1 Prochlorperazine is a dopamine antagonist used to treat nausea, vomiting, and migraine and can cause acute dystonic reaction in 5% of patients.2 Risk factors include male sex, history of acute dystonia, cocaine use, and age < 19 years. Pathogenesis involves dopamine blockade in the basal ganglia, resulting in an imbalance of dopamine and acetylcholine neurotransmitters and increased cholinergic activity.3Signs and symptoms include sudden, involuntary muscle contractions and spasms of the face, neck, tongue, and limbs, which can cause abnormal postures/movements such as arching of the back, twisting of the neck, or rolling of the eyes. Other symptoms may include muscle rigidity or difficulty speaking and swallowing.4Diagnosis is based on a consistent history and the presence of characteristic signs and symptoms. The differential includes acute akathisia, tardive dyskinesia, seizure disorder, tetanus, anticholinergic toxicity, psychogenic nonepileptic seizures, neuroleptic malignant syndrome, and stroke, among others. Studies such as EEG and CT/MRI are usually not necessary but may be ordered if there is suspicion for seizure activity or structural abnormalities, respectively.Treatment involves discontinuation of the medication and administration of an anticholinergic agent such as benztropine or diphenhydramine. Benzodiazepines such as lorazepam may also control symptoms.5
Conclusions: Given the relatively high prevalence of this condition and the common use of phenothiazine derivatives as antiemetics, it is important that the general internist be familiar with acute dystonic reaction as a potential adverse effect. Since the differential is broad, early recognition of this condition can avoid unnecessary and potentially harmful diagnostics and treatments.
