Diltiazem

CARDIZEM is indicated for the management of chronic stable angina and angina due to coronary artery spasm.

Mechanisms of Action Although precise mechanisms of its antianginal actions are still being delineated, CARDIZEM is believed to act in the following ways: Angina Due to Coronary Artery Spasm: CARDIZEM has been shown to be a potent dilator of coronary arteries both epicardial and subendocardial. Spontaneous and ergonovine-induced coronary artery spasms are inhibited by CARDIZEM. Exertional Angina: CARDIZEM has been shown to produce increases in exercise tolerance, probably due to its ability to reduce myocardial oxygen demand. This is accomplished via reductions in heart rate and systemic blood pressure at submaximal and maximal exercise workloads. In animal models, diltiazem interferes with the slow inward (depolarizing) current in excitable tissue. It causes excitation-contraction uncoupling in various myocardial tissues without changes in the configuration of the action potential.

Exertional Angina Pectoris Due to Atherosclerotic Coronary Artery Disease or Angina Pectoris at Rest Due to Coronary Artery Spasm: Dosage must be adjusted to each patient’s needs. Starting with 30 mg four times daily, before meals and at bedtime, dosage should be increased gradually (given in divided doses three or four times daily) at 1- to 2-day intervals until optimum response is obtained. Although individual patients may respond to any dosage level, the average optimum dosage range appears to be 180 to 360 mg/day. There are no available data concerning dosage requirements in patients with impaired renal or hepatic function. If the drug must be used in such patients, titration should be carried out with particular caution.

CARDIZEM is contraindicated in: Patients with sick sinus syndrome except in the presence of a functioning ventricular pacemaker Patients with second- or third-degree AV block except in the presence of a functioning ventricular pacemaker Patients with hypotension (less than 90 mm Hg systolic) Patients who have demonstrated hypersensitivity to the drug Patients with acute myocardial infarction and pulmonary congestion documented by x-ray on admission

Cardiac Conduction: CARDIZEM prolongs AV node refractory periods without significantly prolonging sinus node recovery time, except in patients with sick sinus syndrome. This effect may rarely result in abnormally slow heart rates (particularly in patients with sick sinus syndrome) or second- or third-degree AV block (six of 1243 patients for 0.48%). Concomitant use of diltiazem with beta-blockers or digitalis may result in additive effects on cardiac conduction. A patient with Prinzmetal’s angina developed periods of asystole (2 to 5 seconds) after a single dose of 60 mg of diltiazem. Congestive Heart Failure: Although diltiazem has a negative inotropic effect in isolated animal tissue preparations, hemodynamic studies in humans with normal ventricular function have not shown a reduction in cardiac index nor consistent negative effects on contractility (dP/dt).

Serious adverse reactions have been rare in studies carried out to date, but it should be recognized that patients with impaired ventricular function and cardiac conduction abnormalities usually have been excluded. In domestic placebo-controlled angina trials, the incidence of adverse reactions reported during CARDIZEM therapy was not greater than that reported during placebo therapy. The following represent occurrences observed in clinical studies of angina patients. In many cases, the relationship to CARDIZEM has not been established. The most common occurrences from these studies, as well as their frequency of presentation, are edema (2.4%), headache (2.1%), nausea (1.9%), dizziness (1.5%), rash (1.3%), and asthenia (1.2%).

Due to the potential for additive effects, caution and careful titration are warranted in patients receiving CARDIZEM concomitantly with any agents known to affect cardiac contractility and/or conduction. Pharmacologic studies indicate that there may be additive effects in prolonging AV conduction when using beta-blockers or digitalis concomitantly with CARDIZEM. Diltiazem is both a substrate and an inhibitor of the Pg-p and cytochrome P450 3A4 enzyme system which may affect exposure to diltiazem and concomitant drugs metabolized by those pathways. Patients with renal and/or hepatic impairment may be particularly at risk of exposure changes. Anesthetics: The depression of cardiac contractility, conductivity, and automaticity, as well as the vascular dilation associated with anesthetics, may be potentiated by calcium channel blockers.

Store at 25°C (77°F), excursions permitted to 15° to 30°C (59° to 86°F).