Commenting on the study, Dr. Joseph Izzo of the American Heart Association advised that diabetic patients taking calcium-channel blockers "...should not panic and stop medication without consulting a physician." However, he does advise such patients to speak with their physicians "...about choosing another type of high blood pressure drug, or (using) the calcium antagonist in combination with other agents..."
Among the most common classes of drugs prescribed for hypertension are the calcium-channel blockers -- which dilate blood vessels to reduce blood pressure -- and ACE inhibitors, which basically limit the pressure exerted by the heart on the circulatory system. A team of researchers in Denver, Colorado, investigated the effects of these drugs in patients with type 2 (adult onset, or non-insulin dependent) diabetes.
Dr. Raymond O. Estacio of the University of Colorado Health Sciences Center and colleagues there and elsewhere studied the effects of nisoldipine, a calcium-channel blocker, and enalapril, an ACE inhibitor, in 470 patients with diabetes and hypertension who were enrolled in the Appropriate Blood Pressure Control in Diabetes (ABCD) Trial.
At the end of the five-year study, blood pressure control and the prevalence of heart disease risk factors were similar between the two groups of patients. But the risk of a heart attack was increased 9.5-fold in diabetic patients prescribed nisoldipine.
The American Heart Association says in a statement that the findings provide additional proof "...that calcium antagonists (preferred term for calcium-channel blockers) may pose risks for certain people, including those with diabetes and coronary heart disease." Moreover, the new data shows that these risks are not restricted to patients taking short-acting drugs, since nisoldipine is a long-acting formulation.
However, the Denver researchers also point out that their "... results should be interpreted cautiously." For example, the observed increased risk of heart attack in diabetic patients taking nisoldipine may be the result of a protective effect of enalapril, rather than a deleterious effect of nisoldipine. Regardless, "...the difference between the two study medications was still striking after adjustment for other variables that may influence the..." risk of heart attack (myocardial infarction), Estacio's group reports.
The investigators conclude, based on these data, that "...an ACE inhibitor is the preferred antihypertensive agent, rather than a... calcium-channel blocker, for the prevention of cardiovascular complications, specifically myocardial infarction, in patients with NIDDM (non-insulin dependent diabetes mellitus)."
In a related editorial, Dr. Jeffrey A. Cutler of the National Heart, Lung, and Blood Institute in Bethesda, Maryland, points out that the Denver team's findings may not be sufficient to change prescribing practices for high blood pressure medications. He suggests that physicians wait until the results of other, large-scale, comparative clinical trials of antihypertensive medications in diabetic patients are available to alter their practices.
Wednesday March 4, 98
SOURCE: The New England Journal of Medicine