Should You Be Taking a Diuretic?
Water pills are recommended for most people
with high blood pressure, but doctors don’t always prescribe
them. Here’s why they should.
Current treatment guidelines state that thiazide diuretics should
be used as initial therapy for most patients with hypertension.
But in many cases, doctors instead prescribe such drugs as ACE
inhibitors, angiotensin II receptor blockers, beta-blockers,
or calcium channel blockers. What is the reason for this disparity,
and how do you know whether you’re getting the best drug
to lower your blood pressure?
What the Guidelines Say
The treatment guidelines, issued by the seventh report of the
Joint National Committee on Prevention, Detection, Evaluation,
and Treatment of High Blood Pressure (JNC 7) in 2003, recommend
using diuretics—either alone or in combination with other
drugs—as first-line therapy in all people with high blood
pressure who are otherwise healthy. But in people with other
health conditions, a diuretic may not be the first choice. For
example, beta-blockers or ACE inhibitors may be the preferred
therapy for those with coronary heart disease or kidney disease,
respectively, although diuretics may also be used. In addition,
diuretics are not appropriate in people who are allergic to them
or have experienced serious side effects from them. But most
other people with hypertension should receive a diuretic.
The JNC 7 guidelines were based on many studies, including the
Antihypertensive and Lipid-Lowering Treatment to Prevent Heart
Attack Trial (ALLHAT)—the largest blood pressure drug study
ever conducted. As reported in 2002 in the Journal of the
American Medical Association (JAMA), the trial compared the
traditional recommended therapy, thiazide diuretics, with two
newer—but considerably more expensive—medications:
a calcium channel blocker and an ACE inhibitor.
Patients in all three groups fared equally well with regard
to the occurrence of nonfatal heart attacks or death from coronary
heart disease. The thiazide diuretic, however, was superior to
the other two drugs in lowering blood pressure and reducing the
risk of cardiovascular complications such as stroke and heart
A 2003 study published in The New England Journal of Medicine reached
a different conclusion. In it, Australian researchers concluded
that initiating therapy with ACE inhibitors instead of diuretics
led to fewer cardiovascular complications and deaths from any
cause, despite similar reductions in blood pressure.
But there are important differences between this study—the
Second Annual Australian National Blood Pressure Study (ANBP2)—and
the ALLHAT study. For example, ALLHAT was much larger, with about
24,000 people; ANBP2 had only 6,000 participants. ALLHAT was
also better designed in that both subjects and researchers were
blinded as to what drugs were being used. In addition, the results
of ANBP2 were less consistent: The beneficial effect of ACE inhibitors
was present in men but not in women.
Furthermore, a comprehensive meta-analysis of 42 trials recently
confirmed the ALLHAT results. The meta-analysis, which was published
in JAMA in 2003, combined data on nearly 200,000 people
randomized to 7 major treatment strategies, including a placebo.
It concluded that low-dose diuretics are the most effective first-line
treatment for preventing cardiovascular deaths and illnesses.
The Cost Factor
In addition to being the most effective first-line treatment,
diuretics are also the least expensive. The average cost of a
prescription for a thiazide diuretic is less than $6, while ACE
inhibitors and calcium channel blockers cost five to six times
Despite these findings, many doctors continue to prescribe newer,
more expensive drugs in place of diuretics. In fact, in an article
published in JAMA in 2004, researchers found that 40%
of doctors’ prescriptions fell outside of the JNC 7 recommendations.
The researchers theorize that doctors may choose these newer
agents based on aggressive marketing campaigns, or on the basis
of studies such as ANBP2 that found ACE inhibitors to be more
effective than diuretics. But nationwide compliance with the
JNC 7 guidelines in prescribing drugs to elderly patients with
hypertension would save about $1.2 billion annually.
The Bottom Line
If you’re being treated for high blood pressure and aren’t
taking a thiazide diuretic, ask your doctor if you should be.
It may be that your doctor has selected a different drug as first-line
therapy because you have a condition such as coronary heart disease,
diabetes, or kidney disease, or you have had a stroke. But most
people need a second drug to control blood pressure adequately.
For people who aren’t already taking one, that drug should
usually be a thiazide diuretic.
Coexisting health conditions aren’t the only factors that
play a part in deciding which drug to prescribe. For example,
ALLHAT found that blacks didn’t respond as well as whites
to ACE inhibitors. This difference may not be as significant
as is commonly believed: A study published in Hypertension in
2004 concluded that whites and blacks respond similarly to common
antihypertensive drugs about 90% of the time. The potential for
intolerable side effects is also a factor. So you and your doctor
may need to experiment with several drugs in order to find the
regimen that works best for you.