Moricizine is a class IC antiarrhythmic drug not very commonly used. Class IC drugs block cardiac sodium channels and has no effect on the action potential.

The class IC drugs are commonly used to maintain sinus rhythm in atrial fibrillation patients. Significant coronary artery disease is a contraindication to their use as this increases the risk of proarrhythmia and sudden cardiac death.

The CAST trial demonstrated increased mortality using encainide, flecainide and moricizine to suppress premature ventricular contractions after an acute coronary syndrome.