Jan. 24, 1996
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
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
-- 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
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
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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