Acute Dystonic Reaction Following a Single 4 mg Dose of Chlorpheniramine in an Adolescent: A Case Report

Abstract

Drug induced dystonia is a bizarre type of adverse drug reaction commonly seen with anti-dopaminergic drugs. It is characterized by involuntary muscle spasm resulting in abnormal movement or posture. We hereby present a case report of acute dystonic reaction in a 14-year-old female after ingestion of 4 mg of chlorpheniramine for common cold. She was brought to the emergency room with complaints of restlessness, spasm of the facial muscles and tongue protrusion five hours after taken the chlorpheniramine tablet. The patient was given 10 milligrams of intramuscular diazepam and was monitored for 24 hours. 

All the symptoms disappeared 20 minutes after administration of diazepam with no relapse of symptoms. She was counseled and discharged home. Chlorpheniramine can trigger acute dystonic reaction even at therapeutic doses. Clinicians should maintain a high index of suspicion when evaluating acute movement disorders and consider antihistamines among potential causes. This is, to our knowledge, the first reported case of acute dystonia induced by a therapeutic dose of chlorpheniramine alone, highlighting the need for close monitoring of drugs including common over the counter medications.