Mexiletine Hydrochloride

Mexiletine hydrochloride is a class IB antiarrhythmic agent that blocks fast voltage-gated sodium channels in cardiomyocytes. During phase 0 of the cardiac action potential, sodium influx dominates to allow cells to reach a depolarized state. Mexiletine antagonizes both open and inactivated sodium channels at a specific receptor site, depressing excitability and slowing conduction predominantly in ventricular cells. As a class IB agent, mexiletine detaches from blocked channels more quickly than other sodium channel blockers, resulting in minimal effect at normal heart rates but accumulating block during faster rates, a property known as positive use dependence. Mexiletine also alters late sodium influx during phase 2 of the action potential, diminishing action potential duration.

Fig. 1 Cellular effects of Mexiletine on the cardiac action potential. (Alhourani N.; et al. 2024)

A novel 3D-printed formulation of mexiletine hydrochloride was developed using semi-solid extrusion technology and subjected to a six-month stability assessment under ICH-recommended storage conditions at 25±2°C and 60±5% relative humidity. The printed tablets retained their physical characteristics including shape and color throughout the evaluation period. No significant deviation in drug content or weight was observed, and no detectable levels of degradation products or impurities were confirmed by validated analytical methods at 0 and 6 months.

Fig. 2 Preparation and characterization of 3D-printed formulation of mexiletine hydrochloride. (Ait Hoummad A.; et al. 2025)