Mexiletine can cause drowsiness, dizziness, tremor, muscle twitching, paresthesias, agitation, delirium, and seizures. High plasma levels can result in diplopia and nystagmus. It can cause abdominal pain, dysphagia, GI bleeding, dry mouth, and altered taste. Drug Interactions Phenytoin, rifampin, and other enzyme inducers lower mexiletine plasma levels. Cimetidine can raise plasma levels by inhibiting it s hepatic metabolism.
Cumulative toxicity is observed with lidocaine and mexiletine used together.
Overdose With an overdose, CNS are the major toxicities. Treatment is supportive with atropine used when bradycardia is present. The patient should take mexiletine with food or an antacid. The patient should avoid changes in diet that could acidify or alkalinize the urine drastically. The usual dose is 200 mg every 8 hours unless rapid control of arrhythmia is needed.