Mexiletine overdose producing status epilepticus without cardiovascular abnormalities.
Few cases of mexiletine overdose have been reported in the literature. The available case reports have invariably noted significant hemodynamic or electrocardiographic abnormalities. A 41-year-old woman, on mexiletine for arrhythmia control, ingested up to 90 of her 200 mg mexiletine tablets in a suicide attempt. She presented to the emergency department awake with a normal blood pressure and pulse. Shortly afterwards, the patient had a generalized motor seizure, which responded after 40 minutes to intravenous diazepam 100 mg, phenobarbital 1 g and pyridoxine 5 g. Recurrent status epilepticus at one hour required an additional 40 mg of diazepam and a loading dose of pentobarbital. During the entire episode, her electrocardiogram remained normal. The patient's mexiletine level was 20 micrograms/mL (therapeutic 1-2 micrograms/mL) and the patient's urine screen was negative for cocaine. Mexiletine is a group Ib antidysrhythmic agent with electrophysiologic effects similar to lidocaine. Mexiletine has a little first pass hepatic metabolism and a large volume of distribution along with a high lipid solubility, and prolonged central nervous system toxicity may be expected. As with lidocaine, the toxic deaths from mexiletine have resulted from hypotension and bradycardia. The patient reported had a significant mexiletine overdose which resulted in convulsive status epilepticus, but was devoid of hemodynamic or electrocardiographic abnormalities.
Nelson
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LS
New York City Poison Center, New York 10016.
Hoffman
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RS
D000328:Adult; D001794:Blood Pressure / Q000187:drug effects; D002319:Cardiovascular System / Q000187:drug effects*; D003975:Diazepam / Q000627:therapeutic use; D062787:Drug Overdose; D004359:Drug Therapy, Combination; D004562:Electrocardiography; D005260:Female; D006801:Humans; D008801:Mexiletine / Q000506:poisoning*; D010634:Phenobarbital / Q000627:therapeutic use; D011674:Pulse / Q000187:drug effects; D011736:Pyridoxine / Q000627:therapeutic use; D012008:Recurrence; D012128:Respiratory Distress Syndrome / Q000139:chemically induced; D013226:Status Epilepticus / Q000139:chemically induced* / Q000188:drug therapy; D013406:Suicide, Attempted
D008801:Mexiletine; D011736:Pyridoxine; D003975:Diazepam; D010634:Phenobarbital