Medications and Drugs

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Pharmacy Author: Omudhome Ogbru, PharmD
Medical and Pharmacy Editor: Jay W. Marks, MD

GENERIC NAME: diltiazem

BRAND NAMES: Cardizem, Dilacor, Tiazac and several others

DRUG CLASS AND MECHANISM: Diltiazem is a drug that is used for treating heart pain (angina), high blood pressure, and abnormal heart rhythms. It belongs to a class of drugs called calcium channel blockers (CCBs), which includes amlodipine (Norvasc), verapamil (Calan, Isoptin), nifedipine (Adalat, Procardia) as well as others. CCBs block the entry of calcium into muscle cells that make up the heart and that surround the arteries. It is the entry of calcium into these cells that causes the cells to contract, allowing the heart to pump blood, and the arteries to narrow. By blocking the entry of calcium, diltiazem decreases the force of contraction of the heart and its rate of contraction. It also relaxes the muscles surrounding the arteries, allowing the arteries to widen (dilate). In order to pump blood, the heart needs oxygen. The harder the heart works, the more oxygen it requires. Angina occurs when the supply of oxygen to the heart is inadequate for the amount of work the heart must do. By dilating arteries, diltiazem reduces the pressure in the arteries into which the heart must pump blood, and, as a result, the heart needs to work less and requires less oxygen. By reducing the heart's need for oxygen, diltiazem relieves or prevents angina. Dilation of the arteries also reduces blood pressure. The FDA approved diltiazem in 1982.

PRESCRIPTION: Yes

GENERIC AVAILABLE: Yes

PREPARATIONS: Tablets (immediate release): 30, 60, 90, and 120 mg. Tablets (extended release): 120, 180, 240, 300, 360, 420 mg. Capsules (extended release): 60, 90, 120, 180, 240, 300, 360, 420 mg. Injection: 5 mg/ml. Powder for injection: 25 mg.

STORAGE: Tablets, capsules and powder for injection should be stored at room temperature, 15-30 C (59-86 F). Solution for injection should be stored at 2-8 C (36-46 F).

PRESCRIBED FOR: Diltiazem is used for treating heart pain (angina), high blood pressure, and abnormal heart rhythms such as atrial fibrillation, atrial flutter and paroxysmal supraventricular tachycardia.

DOSING: Adult oral doses range between 120 and 480 mg daily. Immediate release tablets are administered up to 4 times a day. Extended release formulations are administered once daily at approximately the same time each day and should not be crushed or chewed.

DRUG INTERACTIONS: Administration of diltiazem with digoxin (Lanoxin) can increase digoxin blood levels. Therefore, blood levels of digoxin usually are monitored to avoid toxicity from digoxin. Similarly, concurrent administration of diltiazem with an anti-seizure medication, carbamazepine (Tegretol), can increase blood levels of the seizure medication, and occasionally lead to toxicity. Diltiazem increases blood levels of lovastatin (Mevacor), atorvastatin (Lipitor) and simvastatin (Zocor), possibly increasing the risk of adverse effects. Diltiazem may increase blood levels of buspirone (Buspar), midazolam (Versed), triazolam (Halcion) and diazepam (Valium) by reducing their breakdown and elimination from the body by the liver. This can lead to toxicity from these drugs. Rifampin (Rifamate, Rifadin, Rimactane) reduces the effect of diltiazem by reducing its levels in blood to undetectable levels.