This patient is suffering from a metoclopramide-induced acute dystonic reaction. Treatment of this complication includes IV diphenhydramine or benztropine.
Dystonic reactions are reversible extrapyramidal symptoms that may include involuntary spasms or sustained contractions of the face, neck, torso, pelvis, extremities, and larynx. Medications that block dopamine D2 receptors carry the greatest risk for development of a dystonic reaction, most notably including neuroleptics, antidepressants, and antiemetics. A family history of dystonia increases the risk of developing a reaction; there is likely an underlying genetic predisposition. Diagnosis is typically based on history and clinical presentation. Intravenous anticholinergic agents are the first-line treatment, and symptoms typically resolve rapidly (within 1 hour) after initiation of these agents.
Freudenreich describes a case of acute dystonia caused by an antiemetic. Acute dystonic reactions may range in severity from minor, subtle symptoms to a life-threatening complication. In Freudenreich's case, a 36-year-old female was prescribed prochlorperazine for nausea and developed a sore throat and aphonia as a result of laryngeal dystonia. Severe laryngeal dystonia has the potential to result in asphyxia and death if the airway is compromised during a severe dystonic episode.
Dressler et al. discuss the diagnosis and management of medication-induced acute movement disorders, notably dystonic reactions. These reactions are most commonly caused by dopamine-receptor blocking agents, including antipsychotics and antiemetics. Cranial, pharyngeal, and cervical muscles are typically affected within the first four days of initiating treatment.
Figure A shows a patient with dystonia and torticollis; note the posturing of the extremities as well as how the head is tilted to the patient's right side while the chin is directed up and towards the left. Illustration A is a table listing the common clinical manifestations of an acute dystonic reaction. Illustration B is a chart listing the medications known to precipitate acute dystonic reactions.
Answer 1: Valproic acid is an anti-epileptic and mood stabilizer. This patient is suffering from a medication-induced acute dystonic reaction, and valproate does not have a role in the treatment of this condition.
Answer 2: Haloperidol is a high-potency first generation "typical" antipsychotic and carries an elevated risk of inducing extrapyramidal side effects such as acute dystonia. It does not have a role in the management of acute dystonia.
Answer 3: Diazepam has been used to treat acute dystonic reactions; however, it is typically used as a second line agent after initial therapy with anticholinergic agents has failed.
Answer 5: Botulinum toxin injections have been shown to relieve refractory dystonia. However, in the case of an acute, medication-induced reaction, anticholinergic agents such as benztropine and diphenhydramine are first-line.