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Sustained-Release Isradipine Superior to Sustained-Release Amlodipine for Round-the-Clock Blood Pressure Control: Presented at ASH(HYP)

By Jill Stein

NEW YORK, NY -- May 20, 2003 -- Sustained-release isradipine (SR-I) 10 mg may provide better 24-hour control of blood pressure than does sustained-release amlodipine 10 mg, as evidenced by significantly better sustained decreases in systolic blood pressure.

Michael Ganz, MD, of the Clinical Research Center of Cleveland, Cleveland, Ohio, reported new study results on May 16^th at the 18^th Annual Scientific Meeting of the American Society of Hypertension.

Dihydropyridine calcium channel blockers have been widely used for many years to treat mild to moderate hypertension, Dr. Ganz pointed out. Numerous clinical trials have also shown their efficacy in improving related outcomes such as: fatal and nonfatal myocardial infarction, heart failure, and stroke.

Despite the similarities between these agents, however, recent evidence suggests that not all dihydropyridine calcium channel blockers are equivalent in terms of blood pressure control or incidence of treatment-emergent side effects, such as pedal edema. In particular, sustained-release isradipine has previously been shown to produce lower rates of edema than amlodipine, an intrinsically long-acting dihydropyridine calcium channel blocker.

The present study was undertaken to determine whether substituting sustained-release isradipine for amlodipine improves the antihypertensive response in subjects currently being treated with amlodipine, and to compare the tolerability, particularly of edema, between sustained-release isradipine and sustained-release amlodipine.

One hundred and fourteen patients with mild to moderate hypertension, who had been treated with sustained-release amlodipine (5 or 10 mg qd) for at least 4 months, were eligible for enrollment. The only major exclusion criteria were evidence of coronary heart disease, or congestive heart failure.

Seated cuff blood pressure was measured after a 20-minute period of quiet rest. Blood pressure measurements were made at trough 3 times during the 6-month run-in period, and again 2 weeks before drug substitution. The average of these 4 measurements was used as the baseline blood pressure.

At the end of the run-in period, subjects who were currently treated with amlodipine 5 mg/d were switched to sustained- release isradipine 5 mg/d, and those currently treated with amlodipine 10 mg/d were switched to sustained- release isradipine 10 mg/d. Adjuvant antihypertensive therapy was permitted, provided the drugs and their doses remained stable.

Blood pressure was measured at 2-week intervals during the sustained –release isradipine treatment period. After 6 weeks of treatment with sustained- release isradipine, subjects were switched back to amlodipine at their original dose; blood pressure was evaluated 6 weeks later. At each study visit, subjects were evaluated for clinically evident lower limb edema.

Those treated with sustained-release isradipine 10 mg were found to have significantly lower systolic blood pressure than patients treated with amlodipine 10 mg from 2 weeks through 6 weeks, with levels dropping from 154.4 ± 8.8 mm Hg at baseline to 146.5 ± 7.4 mm Hg at 6 weeks. The sustained-release isradipine treatment groups also had diastolic blood pressure reduced, but the change was not significant.

Among the 5 mg treatment groups, there was no significant change in systolic or diastolic blood pressure. Seven additional patients were adequately controlled while on sustained-release isradipine, primarily because of reductions in systolic blood pressure. Six weeks after returning to amlodipine, blood pressure had returned towards baseline values.

There was a trend to less edema for Caucasian men, although this did not reach statistical significance. There were no other reported differences in side effects.

Dr. Ganz said that the significantly superior antihypertensive effect seen among subjects taking sustained-release isradipine 10 mg/d may confer an important clinical advantage, as subjects in this treatment group tended to be heavier, and to take more medications, making their condition more difficult to control.


[Study title: Efficacy and Safety of Sustained -Release (SR)-Isradipine in Hypertensive Patients Treated With SR-Amlodipine. An Open-Label Drug Substitution Study. Abstract 211]

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