Diltiazem

Diltiazem is a member of the group of drugs known as benzothiazepines , which are a class of calcium channel blockers, used in the treatment of hypertension, angina pectoris, and some types of arrhythmia. It is a class 3 anti-anginal drug, and a class IV antidysrhythmic. It incites very minimal reflex sympathetic changes.

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Diltiazem is a potent vasodilator, increasing blood flow and variably decreasing the heart rate via strong depression of A-V node conduction. Its pharmacolgical activity is somewhat similar to verapamil

Diltiazem is metabolized by and acts as an inhibitor of the CYP3A4 enzyme.

Diltiazem is relatively contraindicated in the presence of sick sinus syndrome, atrioventricular node conduction disturbances, bradycardia, impaired left ventricle function, peripheral artery occlusive disease, chronic obstructive pulmonary disease, and Prinzmetal's angina.

Brand names

• Cardizem®
• Cartia XT®
• Tiazac®
• Tiazac XC®
• Tiamate®
• Tildiem® in particular in Europe
• Adizem®
• Viazem
• Dilatam®

[[Therapeutic Effects:]] Potent vasodilator of coronary vessels.

Vasodilator of peripheral vessels. This reduces peripheral resistance and afterload.

Negative inotropic effect. Diltiazem causes a modest decrease in contractility and reduces myocardium oxygen consumption.

Negative chronotropic effect. Diltiazem causes a modest lowering of heart rate. This effect is due to slowing of the SA node. It results in reduced myocardium oxygen consumption.

Negative dromotropic effect. By slowing conduction through the AV node, diltiazem increases the time needed for each beat. This results in reduced myocardium oxygen consumption.

[[Nontherapeutic Effects and Toxicities:]] Reflex sympathetic response. Caused by the peripheral dilatation of vessels and the resulting drop in BP; the response works to counteract the inotropic, chronotropic and dromotropic effects of diltiazem. Hypotension. Bradycardia. Dizziness. Flushing.

[[Indications:]] Stable (exercise-induced) Angina. Diltiazem increases coronary blood blow and decreases myocardial oxygen consumption, secondary to decreased peripheral resistance, heart rate, and contractility.

Variant Angina. Diltiazem is effective due to its direct effects on coronary dilatation.

Unstable (preinfarction, crescendo) Angina. Diltiazem may be particularly effective if the underlying mechanism is vasospasm. Supraventricular tachycardias. Diltiazem appears to be as effective as verapamil in treating reentrant supraventricular tachycardia.

Atrial fibrillation or flutter.

Hypertension. Because of its vasodilatatory effects, diltiazem is useful for treating hypertension. Calcium channel blockers are well-tolerated, and especially effective in treating low-renin hypertension.

[[ Contraindications and Precautions:]] CHF. Patients with reduced ventricular function may not be able to counteract the inotropic and chronotropic effects of diltiazem, the result being an even higher compromise of function.

SA node or AV conduction disturbances. Use of diltiazem should be avoided in patients with SA or AV nodal abnormalities, because of its negative chronotropic and dromotropic effects Low blood pressure. Patients with systolic blood pressures below 90 mm Hg should not be treated with diltiazem.

Wolff-Parkinson-White syndrome. Diltiazem may paradoxically increase ventricular rate in patients with WPW syndrome because of accessory conduction pathways.

[[Drug Interactions:]] Beta-blockers. I.V. diltiazem should never be used concurrently with a beta-blocker; can result in AV block. Quinidine. Quinidine should not be used concurrently with calcium channel blockers because of reduced clearance of both drugs and potential pharmacodynamic effects at the SA and AV nodes. Miscellaneous Inhibition of hepatic enzymes. Diltiazem and verapamil inhibit hepatic drug metabolizing enzymes, promoting possible drug interactions.