Lenore Gelb
Jan. 24, 1996
(301) 443-3285

The Food and Drug Administration has asked its Cardiovascular and Renal Drugs Advisory Committee to consider recent reports on calcium channel blockers and to suggest what steps if any are needed to improve the safety and effectiveness of these products. The committee will discuss this large, diverse class of drugs on Thursday, Jan. 25. The following can be used to answer questions.

Most calcium channel blockers are approved in the United States for the control of high blood pressure, others are approved to treat different types of angina, and a few are approved to control irregular heartbeats. One is approved to improve the neurological outcome after a certain type of stroke.

Calcium channel blockers lower blood pressure by changing the movement of calcium in and out of cells in blood vessels and the heart.

The data to be presented to the advisory committee will include the following:

-- Data suggesting that certain patients with high blood pressure who were given immediate-release formulations of certain calcium channel blockers (nifedipine, diltiazem and verapamil) were more likely to suffer heart attacks than patients who received other medications, such as diuretics or beta-blockers. Because these data were not collected in randomized clinical trials, a critical question is whether the increased risk of heart attack may have been due to factors other than the drug treatment.

-- Results from randomized controlled trials in which calcium channel blockers were given to patients who were not necessarily hypertensive, but who were at a much higher than average risk of heart attack.

-- A meta-analysis combining the results of 16 studies of patients at high risk for heart attacks which found an increased incidence of death in patients who received the highest doses of an immediate-release calcium channel blocker.

-- Epidemiological interpretation of the presented data highlighting the limitations of studies other than randomized clinical trials.

The committee will be asked to recommend regulatory actions based on the studies presented. These recommendations could include making no changes, amending labeling on approved drugs, asking manufacturers to do new studies, and removing certain indications from approved drugs.

Physicians legally may prescribe drugs for off-label uses, and some of the calcium channel blockers have been prescribed extensively for purposes other than those for which they were approved and promoted. For example, immediate-release formulations of nifedipine and diltiazem have never been approved to control high blood pressure, but have been extensively prescribed for this purpose during the 1980s.

Some of the calcium channel blockers act quickly and are rapidly eliminated from the body. These short-acting, immediate- release formulations must be taken three or four times a day. Other formulations are sustained release and can be taken only once a day. Along with this convenience, it is possible that patients on sustained-release products may also avoid sharp peaks of the drug's effects.

Pending possible FDA action on the recommendations of the advisory committee, patients taking calcium channel blockers should continue to follow the advice of their physicians.

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