Research Updates in Kidney and Urologic Health
Drugs Found To Protect the Kidneys
On the advice of an independent data and safety monitoring board, the
National Institutes of Health (NIH) called an early halt to one arm of
a study after finding that people with kidney disease and protein in their
urine were more likely to postpone kidney failure if they took either
an ACE (angiotensin-converting enzyme) inhibitor or a beta blocker rather
than a calcium channel blocker (CCB).
Compared with the CCB amlodipine (Norvasc), the ACE inhibitor ramipril
(Altace) or the beta blocker metoprolol (Toprol) significantly reduced
the risk of kidney failure in a group of patients who had at least 1 gram
of protein in a 24-hour urine sample when they joined the African American
Study of Kidney Disease and Hypertension (AASK). Blood pressures were
comparable.
Paradoxically, CCBs are one of two first-line choices for high blood
pressure in African Americans1; 62 percent of AASK patients took CCBs
before joining the study. The type of CCB used in AASK, a dihydropyridine,
was found in this study and in other recent studies to be associated with
increases in protein in the urine. Such increases are linked to advancing
kidney disease.
ACE inhibitors have been preferred for kidney disease of diabetes since
1994. Subsequent studies of other kidney diseases have found an association
between protein in the urine and protection by ACE inhibition. Considered
with the results of these other studies, AASK extends the value of ACE
inhibitors to kidney disease of hypertension, at least for people with
protein in their urine.
"This trial will have a tremendous effect on how we care for people,"
predicts Dr. Janice Douglas, director of the hypertension division at
Case Western Reserve in Cleveland and chair of the study's steering committee.
"Most striking to me is the correlation between elevated urine protein
and faster disease progression, something we can look for in all people
with kidney disease," she explains. Dr. Douglas presented the study at
the 33rd annual meeting of the American Society of Nephrology last October
in Toronto.
Dr. Lawrence Agodoa, a kidney specialist and AASK director at NIH, cautions
patients to keep taking prescribed blood pressure medicine until they
have worked out an alternative with their doctor. "Calcium channel blockers
are good for controlling high blood pressure, and patients are not in
immediate risk," he explains.
AASK will continue to compare the ACE inhibitor
and beta blocker and to test whether a lower blood pressure target of
125/75 is more protective of the kidneys than 140/90. A CCB may be used
as a secondary treatment if needed to reach blood pressure goals. AASK enrolled 1,094 African Americans at 21 centers and is scheduled
to end in the fall of 2001.
African Americans make up 12.6 percent of
the U.S. population but 29.8 percent of those treated for kidney failure.
Hardest hit are African Americans between the ages of 25 and 44, who are
20 times more vulnerable to hypertension-related kidney failure than whites
in the same age group. Better management of high blood pressure has led
to fewer strokes and heart disease, but kidney failure is still increasing.
Reference
1. The sixth report of the Joint National Committee on Prevention, Detection,
Evaluation, and Treatment of High Blood Pressure (JNC-VI). Archives
of Internal Medicine. 1997;157:2413–2446.
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