CONTACT:  NHLBI Press Office
(301) 496-4236

August 22, 1995


NHLBI Prepared Statement for Physicians

CALCIUM CHANNEL BLOCKERS FOR HYPERTENSION


A case-control study funded by the National Heart, Lung, and
Blood Institute (NHLBI) and published in the August 23/30
issue of the "Journal of the American Medical Association"
found that high blood pressure patients taking a calcium
channel blocker may have a greater risk of heart attack than
patients taking a diuretic or a beta blocker.

This study, conducted at the University of Washington,
raises some concerns about the relative safety of calcium
channel blockers that can only be conclusively answered in a
large-scale, long-term randomized clinical trial.  Such a
trial is currently underway, but since the results are not
yet available, the NHLBI is preparing a statement for
physicians and other health professionals to help guide them
as they advise their patients about the safety of calcium
channel blockers.  This statement will refine the
Institute's position on calcium channel blockers.  It will
be based on a review conducted by an NHLBI-convened Ad Hoc
Panel on Calcium Channel Blockers which met in June 1995. 
The panel reviewed the available scientific evidence on the
safety of this class of drugs.  The NHLBI statement will be
completed and available to the public in early September.

In the University of Washington study, the investigators
found a 60 percent higher "relative risk" of heart attack
among the patients taking a calcium channel 
blocker compared to those taking a diuretic or a beta
blocker.  In addition, higher doses of calcium channel
blockers were associated with greater risk.  All of the
calcium channel blockers in this study (nifedipine,
diltiazem, and verapamil) were of the short-acting type
requiring several daily doses.  If this study's results are
confirmed, the short-term risk of heart attack for an
individual from calcium channel blockers would be low.  For
every 1000 high blood pressure patients treated with 
diuretics or beta blockers for one year, about 10 would be
expected to have a heart attack within a year.  The
University of Washington study suggested that if the
patients were taking calcium channel blockers, 16 rather
than 10 might suffer a heart attack.

In a "case control" study such as this, scientists review
medical records to identify patients or "cases" with a
disease and then compare certain characteristics of these
"cases" with a similar group of "control" patients.  In the
University of Washington study, scientists identified
patients with hypertension at a health maintenance
organization (HMO) and then used computerized pharmacy
records to obtain information on the drugs being taken. 
Women with hypertension who had suffered heart attacks
between 1986 and 1993 and men with hypertension who had
heart attacks between 1989 and 1993 were compared with a
"control" group of high blood pressure patients at the HMO
who had not had heart attacks.

A case control study, although useful, cannot provide
definitive information on the effectiveness and long-term
safety of a class of drugs.  Even with rigorous statistical
procedures to make the cases and controls as similar as
possible, there may be unknown and important differences
which can account for the findings.  For example, there may
be differences related to the reasons why a specific drug
was chosen.  Only if the University of Washington's study's
findings are confirmed in a long-term randomized clinical
trial, will we know for sure that this class of drugs is
tied to an increased risk of heart attack.  The conclusions,
even if validated in a clinical trial, would relate
primarily to patients being treated for hypertension,
because patients who had congestive heart failure or a prior
heart attack were excluded from the study. 

Hypertensive patients currently taking calcium channel
blockers should not stop taking their medication and should
discuss any concerns with their physicians.  As always, the
choice of drug for a particular patient is based on that
individual's condition and an assessment of the drug's risks
and benefits for that patient.  Current treatment guidelines
for physicians, which are included in the fifth Report of
the Joint National Committee on Detection, Evaluation, and
Treatment of High Blood Pressure (JNC V), recommend
diuretics and beta-blockers as preferred agents for high
blood pressure.  According to the JNC V, a document produced
by the NHLBI's National High Blood Pressure Education
Program, calcium channel blockers and other alternative
drugs should be reserved for special situations or when
diuretics and beta blockers have proved unacceptable or
ineffective.

The JNC V noted an urgent need to study the long-term
effectiveness and safety of the alternative drugs in
reducing deaths and disability for cardiovascular disease. 
In pursuit of this goal, the NHLBI has initiated the
Antihypertensive and Lipid-Lowering Treatment to Prevent
Heart Attack Trial (ALLHAT).  The hypertension component of
ALLHAT will compare the effects of a diuretic, an ACE
inhibitor, a calcium channel blocker, and an alpha blocker
in older hypertensive patients.
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