Background. Mexiletine, a class IB antiarrhythmic, is a structural analog of lidocaine. Our knowledge of mexiletine overdose is based on lidocaine overdose reports. Only a few cases of mexiletine overdose have been reported, including fatal overdoses. Mexiletine toxicity primarily affects the central nervous, cardiovascular, and gastrointestinal systems.

Case. A 16-year-old female was brought to our hospital by ambulance after taking an unknown dose of mexiletine in a suicide attempt. Ventricular fibrillation developed while in the ambulance; cardiopulmonary resuscitation was started and spontaneous circulation returned within 1 min. The patient had been taking oral mexiletine for 1 month to treat primary erythromelalgia. Her vital signs were normal, but she was unconscious. Following gastric lavage she was transferred to the pediatric intensive care unit. Midazolam and levetiracetam were required due to uncontrolled seizures. During the first hour of hospitalization, severe dyskinesia characterized by abnormal involuntary large hyperkinetic movements in all 4 extremities was observed and successfully treated with 2 doses of intravenous biperiden. The patient was discharged on day 6 of hospitalization.

Conclusions. Mexiletine overdose can be life-threatening. In addition to rapid and effective resuscitation, rapid identification and management of cardiovascular and central nervous system manifestations are key to preventing morbidity and mortality. The presented case had severe dyskinesia that was successfully treated with repeated doses of biperiden. Biperiden did not cause arrhythmia. Based on the presented case, we think biperiden should be considered for the treatment of movement disorders in cases of mexiletine overdose.

Keywords: biperiden, dyskinesia, intoxication, mexiletine, poisoning