NCIt definition : The hydrochloride salt form of mexiletine, a local anesthetic and antiarrhythmic (Class
IB) agent structurally related to lidocaine. Mexiletine exerts its antiarrhythmic
effect by inhibiting the inward sodium current in cardiac cells, thereby reducing
the rate of rise of the cardiac action potential (phase 0) and decreases automaticity
in the Purkinje fibers. This slows nerve impulses in the heart and stabilizes the
heartbeat. Mexiletine's anesthetic activity is due to its ability to block sodium
influx in peripheral nerves, thereby reducing the rate and intensity of pain impulses
reaching the central nervous system.;