By: Thomas Pickering, MD, DPhil, FRCP, Director of Integrative and Behavioral Cardiology Program
of the Cardiovascular Institute at Mount Sinai School of Medicine, New York.

Calcium channel blockers (also known as calcium antagonists) are widely prescribed for the treatment of hypertension and are highly effective. They have recently come under fire because of several reports that they can increase the risk of having a heart attack, but it appears that this was attributable to the shorter acting form of nifedipine, and that the longer acting and newer calcium channel blockers are safe in this respect. Now comes a report that raises further doubts. In this study, which was conducted as part of the Established Populations for Epidemiologic Studies of the Elderly, 1,636 elderly hypertensive people (aged 68 or more) in three US communities were followed for seven years. They were divided into three groups, according to whether they were taking calcium channel blockers, ACE inhibitors or beta blockers to lower their blood pressure. The principal finding was that patients treated with calcium channel blockers were nearly twice as likely to experience gastro-intestinal bleeding (i.e. from the stomach or bowels) as those treated with the other drugs. When the different calcium channel blockers were examined, it was found that the increased risk was related to the use of verapamil and diltiazem but not to nifedipine.

Doctor's comments

One of the effects of calcium channel blockers is that they inhibit the action of blood platelets, and hence, prevent blood clots from forming. Since blood clots in the arteries may trigger strokes and heart attacks, calcium channel blockers could in theory help to prevent them, although this has not been proven. The downside of this effect is that they can also increase the risk of bleeding, as shown in this study. In this respect they resemble aspirin, which also inhibits blood platelets and is the number one cause of drug-induced stomach bleeding. Unlike calcium channel blockers, however, aspirin has been proven to prevent strokes and heart attacks in high-risk patients. The study implies that calcium channel blockers should be used with caution in elderly hypertensives, but if there is no history of conditions that might increase the risk of intestinal bleeding (such as stomach ulcers, diverticulosis, or polyps), and calcium channel blockers are needed to control the blood pressure, they can continue to be used.

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