indication

Used to treat irregular heartbeats (arrhythmias) and maintain a normal heart rate.

pharmacology

Moricizine is used to treat irregular heartbeats (arrhythmias) and to maintain a normal heart rate. It acts on the heart muscle to improve the heart's rhythm. Moricizine has potent local anesthetic activity and membrane stabilizing effect. Decreases excitability, conduction velocity, and automaticity as a result of slowed atrioventricular (AV) nodal and His-Purkinje conduction. Decreases the action potential duration (APD) in Purkinje fibers; also decreases the effective refractory period (ERP) but to a lesser extent than the APD, so the ERP/APD ratio is increased. Decreases the maxiumum rate of Phase 0 depolarization (V max ), but does not affect action potential amplitude or maximum diastolic potential. Does not affect atrial, AV nodal, or left ventricular refractory periods and has minimal effect on ventricular repolarization (evidenced by the overall decrease in JT interval). Has no effect on sinoatrial (SA) nodal or intra-atrial conduction and only minimal effect on sinus cycle length and sinus node recovery time. In the Vaughan Williams classification of antiarrhythmics, moricizine is considered to be a class I agent. It has properties of class IA, IB, and IC agents but does not clearly belong to any of the three subclasses. It has less effect on the slope of phase 0 and a greater effect on action potential duration and effective refractory period than class IC agents.

mechanism of action

Moricizine works by inhibiting the rapid inward sodium current across myocardial cell membranes.

toxicity

Symptoms of overdose include vomiting, unconsciousness, and severe low blood pressure.

biotransformation

Hepatic and extensive, to at least 26 metabolites, none accounting for as much as 1% of the administered dose. Two metabolites may be pharmacologically active but are present in extremely small quantities. Moricizine induces its own metabolism (it induces hepatic cytochrome P-450 activity).

absorption

Well absorbed, absorption is complete within 2 to 3 hours. Significant first-pass metabolism results in an absolute bioavailability of approximately 38%. Administration within 30 minutes after a meal slows the rate, but does not affect the extent of absorption, although peak plasma concentrations are reduced.

half life

2 hours (range 1.5-3.5 hours).

route of elimination

Less than 1% of orally administered Ethmozine® is excreted unchanged in the urine. Approximately 56% of the administered dose is excreted in the feces and 39% is excreted in the urine.

drug interactions

Diltiazem: Increased effect/toxicity of moricizine

Ranolazine: Possible additive effect on QT prolongation

Telithromycin: Telithromycin may reduce clearance of Moricizine. Consider alternate therapy or monitor for changes in the therapeutic/adverse effects of Moricizine if Telithromycin is initiated, discontinued or dose changed.

Voriconazole: Voriconazole, a strong CYP3A4 inhibitor, may increase the serum concentration of moricizine by decreasing its metabolism. Monitor for changes in the therapeutic and adverse effects of moricizine if voriconazole is initiated, discontinued or dose changed.