Toxicity Potential of Oral Lidocaine in a Patient Receiving Mexiletine

OBJECTIVE: To report a case of toxicity from orally administered lidocaine in a patient with cardiomyopathy receiving concurrent mexiletine therapy. DATA SOURCES: Case reports, review articles, and studies identified by search of the MEDLINE database and Current Contents. STUDY SELECTION: All reports of toxicity from orally administered lidocaine were reviewed. DATA SYNTHESIS: Lidocaine, a local anesthetic, is widely used to treat cardiac arrhythmias. Toxicity with the parenteral form occurs frequently. In contrast, there are few reports of toxicity with oral lidocaine, most of them occurring in children receiving large doses relative to body weight. We report a case of intoxication in an adult with severe cardiomyopathy and concurrent mexiletine therapy who received only two doses of oral lidocaine. CONCLUSIONS: Although it is rarely reported in adults, clinicians must be alert to the possibility of toxicity from orally administered lidocaine. This is most likely to occur in patients with conditions known to reduce lidocaine clearance, when higher-than-usual doses are administered, or when concurrent therapy with oral lidocaine analogs may be present.