Tiazac (diltiazem hydrochloride)

The following drug information is obtained from various newswires, published medical journal articles, and medical conference presentations.

Approval Status:

Approved February 1996

Specific Treatments:


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General Information

Tiazac has been approved as a treatment for hypertension. The once-daily calcium channel blocker reduces blood pressure of hypertensive subjects. Through its extended-release, osmotic diffusion system of concentrated diltiazem beads, Tiazac delivers smooth 24-hour plasma levels, which are highly correlated with blood pressure measurements. When properly dosed, Tiazac provides smooth and predictable 24-hour blood pressure control. A greater blood pressure reduction is achieved with Tiazac when blood pressure is at its highest, yet Tiazac achieves blood pressure reduction without causing hypotension during periods of lower blood pressure.

Tiazac, a highly concentrated formulation of diltiazem, enables more drug to be contained inside a smaller capsule. This formulation allows for both smaller capsules for a given dosage, relative to the same dose of other once-daily diltiazem products, and for five dosage strengths: 120, 180, 240, 300, and 360 mg.

Tiazac, as with all diltiazem formulations, should not be used in subjects with severe hypotension (less than 90 mm Hg systolic), acute myocardial infarction and pulmonary congestion documented by x-ray on admission, subjects with sick sinus syndrome or 2nd/3rd-degree AV block (unless used with a pacemaker), and subjects who have demonstrated hypersensitivity to the drug. This drug should be used with caution in subjects with impaired kidney, liver, or heart function.

Clinical Results

In a major comparative trial of single-drug therapy for hypertension, diltiazem showed blood pressure control greater than or comparable to that of six other antihypertensives from different drug classes. African-American patients in the study responded especially well to diltiazem therapy, while Caucasians responded well to all drug classes.

Doses of Tiazac up to 360 mg exhibited a side-effect profile similar to that of the lower doses, and similar to placebo. Tiazac can be safely dosed up to 540 mg. In clinical trials, absorption of Tiazac was not affected by food intake: Tiazac can be taken with or without food, even high-fat meals.

Tiazac showed no clinically significant changes in ECG readings, no increases in 2nd or 3rd-degree AV heart block and no more than a slight decrease in heart rate.

Side Effects

Tiazac was well tolerated in clinical trials. The most commonly reported side effects were headache, peripheral edema, pain, dizziness, and asthenia.

Mechanism of Action

Tiazac produces its antihypertensive effect primarily by relaxation of vascular smooth muscle and the resultant decrease in peripheral vascular resistance. The magnitude of blood pressure reduction is related to the degree of hypertension: thus hypertensive individuals experience an antihypertensive effect, whereas there is only a modest fall in blood pressure in normotensives.

Additional Information

Blood pressure normally varies throughout the day and night and is influenced by the subject’s own circadian rhythm and external stimuli. In hypertensive subjects, blood pressure needs 24-hour control to achieve blood pressure levels that approach treatment goals.