Moracizine[1] or moricizine, sold under the trade name Ethmozine, is an antiarrhythmic of class IC.

[2] It was used for the prophylaxis and treatment of serious and life-threatening ventricular arrhythmias,[3] but was withdrawn in 2007 for commercial reasons.

A clinical study has shown that moracizine is slightly less effective than encainide or flecainide in suppressing ventricular premature depolarizations.

[citation needed] In the Cardiac Arrhythmia Suppression Trial (CAST), a large study testing the influence of antiarrhythmics on mortality, showed a statistically non-significant increase of mortality from 5.4 to 7.2% under moracizine.

Alkylation of morpholine by nucleophilic substitution at the sidechain chlorine yields moricizine.