Moricizine is an antiarrhythmia agent which is used primarily for ventricular rhythm disturbances.

Moricizine would exert an antiarrhythmic action on atrial myocytes, as well as on ventricular myocytes, by blocking Na+ channels with a high affinity to the inactivated state and slow dissociation kinetics. Moricizine induced the tonic block of INa with the apparent dissociation constant (Kd,app) of 6.3 uM at -100 mV and 99.3 microM at -140 mV. Moricizine works by inhibiting the rapid inward sodium current across myocardial cell membranes. Moricizine at 30 uM shifted the h infinity curve to the hyperpolarizing direction by 8.6 +/- 2.4 mV. Moricizine also produced the phasic block of INa, which was enhanced with the increase in the duration of train pulses, and was more prominent with a holding potential (HP) of -100 mV than with an HP of -140 mV.