The National Institutes of Health (NIH) called an early halt to one arm of a study on the advice of an independent data and safety monitoring board after finding that people with kidney disease and protein in their urine were more likely to postpone kidney failure using either an ACE inhibitor or a beta blocker than a calcium channel blocker (CCB).
The ACE inhibitor ramipril (Altace®) or the beta-blocker metoprolol (Toprol®) significantly reduced the risk of kidney failure compared to the CCB amlodipine (Norvasc®) in a group of patients who had at least one gram of protein in a 24-hour sample of urine when they joined the African American Study of Kidney Disease and Hypertension (AASK). Blood pressures were comparable.
Paradoxically, CCBs are one of two first-choice medicines for high blood pressure in African Americans;1 62 percent of AASK patients were on 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. Protein increases are linked with 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 the 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 will present the study at the 33rd annual meeting of the American Society of Nephrology in Toronto.
Dr. Lawrence Agodoa, a kidney specialist and NIH director of AASK, 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. The 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 people treated for kidney failure. Hardest hit are blacks ages 25 to 44, who are 20 times more vulnerable to hypertension-related kidney failure. Better management of high blood pressure has led to fewer strokes and heart disease, but kidney failure is still increasing.
- The number for the ASN Press Room in Toronto is (416) 585-3715.
- AASK is funded in part by the NIH Office of Research on Minority Health.
- Study drugs are provided by Pfizer, Monarch/King Pharmaceuticals, and Astra USA.
1. The 6th Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure, Nov. 1997.