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Study inconclusive on channel blockers


My doctor has been treating my high blood pressure with a calcium channel blocker drug for a number of years. I am concerned by newspaper articles that described an increase in heart attacks in people taking this kind of drug. Do you think I should stop taking this drug?

You should not stop taking the medication, but should speak to your doctor about your worries.

The controversy about calcium channel blocker drugs began earlier this year with a talk at a medical meeting that was followed by publication of the data used to reach the conclusions made in the talk. The data showed that the risk of a heart attack was increased among users of calcium channel blockers compared with those taking other medication for their hypertension.

The data involved a comparison between two groups of patients in Seattle taking medications to treat hypertension. Patients in Group 1 had suffered a heart attack; those in Group 2 had not. The number of heart attacks in Group 1 was 60 percent greater in those taking calcium channel blockers compared with those using other drugs (diuretics, beta blockers, ACE inhibitors). Also, the apparent risk of a heart attack increased as the dose of the calcium channel blockers increased.

L Several factors raise important doubts about these findings.

First, there were major differences between the two groups of patients in the study. In the group that had heart attacks were twice as many patients with several major risk factors for heart attacks (cigarette smoking, diabetes, angina and leg pain due to narrowed arteries of the lower extremities) as in the group that did not have heart attacks.

It may have been the increased risk of a heart attack that led the doctors to prescribe a calcium channel blocker, rather than another antihypertensive drug. If this were the case, the calcium channel blockers would not have caused the higher rate of heart attacks in those taking this type of medication. The limitations of this study do not allow a clear interpretation of this medication.

It is also worth noting that the study suggesting an increased risk of heart attacks with calcium channel blockers examined only the effects of short-acting drugs, whereas long-acting calcium channel blockers are now more commonly prescribed. There currently is a large study comparing the risks and benefits of all the classes of antihypertensive drugs, but the results will not be available until after 2000.

The most recent national task force on hypertension cited at least two reasons for its recommendation that diuretics and beta blockers remain the first-choice drugs for the treatment of hypertension. The possible risks and benefits of these drugs are better known than those of the newer calcium channel blockers and ACE inhibitors. Diuretics and beta blockers also are less expensive than the newer drugs.

On the other hand, there are several reasons that a calcium channel blocker or ACE inhibitor might be the preferred treatment in a given individual; and the available evidence should not make patients fearful when their doctors prescribe a calcium channel blocker for their hypertension. (It is always reasonable, however, to ask why a particular drug was selected.)

Dr. Margolis is professor of medicine and biological chemistry at the Johns Hopkins School of Medicine.

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