Abstract: Objective To explore the causality, possible mechanism and influencing factors of such adverse events as oral and lip numbness associated with mexiletine so as to provide data for precautions. Methods Literature related to adverse events of oral and lip numbness caused by mexiletine were retrieved from such databases as Wanfang, CNKI, VIP, PubMed and VigiBase before being analyzed. The causality of single cases or a series of cases was explored. Results As of April 26, 2020, there were 10 cases of oral and lip numbness associated with mexiletine: 3 cases from online consultation, 3 cases from VigiBase, and 4 cases from literature. Causal analysis by Naranjo criteria delivered a causality score that supported causality between mexiletine and adverse reactions. The possible mechanism was that mexiletine was structurally similar to lidocaine, so it had a local anesthetic effect, which could cause oral and lip numbness. The onset time of oral and lip numbness ranged from shortly after administration to 5 days after administration, but the patients recovered after withdrawal. Routes of administration might play a role. Conclusion Mexiletine can cause oral and lip numbness, which is related to the local anesthetic effect. Therefore, oral preparations should be taken as a whole along with beverages or foods rather than being chewed to prevent adverse reactions.

Key words: mexiletine, oral and lip numbness, adverse drug reaction