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Two Drugs Are No More Effective Than One to Treat Common Kidney Disease

NIH studies find limited kidney benefit from more rigorous blood pressure treatment

Using two drugs was no more effective than a single drug in slowing disease progression in people with autosomal dominant polycystic kidney disease (ADPKD), according to two studies funded by the National Institutes of Health (NIH). One of the studies also showed that rigorous blood pressure treatment slowed the growth of kidney cysts, a marker of ADPKD, but had little effect on kidney function compared with standard blood pressure treatment.

The results of the HALT-PKD Clinical Trials Network studies were published online November 15 in two papers in the New England Journal of Medicine to coincide with their presentation at the American Society of Nephrology annual meeting.

The HALT-PKD trial enrolled volunteers to test whether a combination of commonly used FDA-approved drugs, lisinopril and telmisartan, could shrink kidney cysts and therefore slow progression of ADPKD, a genetic disorder characterized by the growth of fluid-filled cysts in the kidneys. Within the trial, one study examined 558 people with early-stage ADPKD and relatively healthy kidneys. The  other study treated 486 people with more advanced disease and decreased kidney function. In each study, half of the participants were randomly assigned to receive lisinopril and telmisartan, while the other half received lisinopril plus a placebo. In both studies, adding the second drug did not change kidney function or the rate of increase in kidney cyst size.

In the study of people with early ADPKD and healthy kidneys, the researchers also tested whether decreasing blood pressure below usual targets would slow the progression of ADPKD and preserve kidney function. Hypertension is a common and damaging effect of ADPKD. Half of the participants were assigned to a standard blood pressure group (between 120–130 over 70–80), and half to a lower blood pressure group (between 95–110 over 60–75) but still within the normal range.

Participants in the lower blood pressure group received more rigorous treatment, taking more medication to maintain a lower blood pressure. These patients had a 14% decrease in kidney cyst size compared with those in the standard blood pressure group. However, kidney function –– measured by the estimated glomerular filtration rate –– was approximately the same as that of the standard group at the end of the trial, yielding no clinical benefit. Approximately 15% more of the people in the lower blood pressure group experienced lightheadedness and dizziness.

ADPKD is the most common type of polycystic kidney disease, representing 90% of the approximately 600,000 cases in the U.S. PKD is the fourth leading cause of kidney failure.

Source: NIH; November 17, 2014.

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