New drug linked to fewer deaths among kidney patients undergoing hemodialysis
University of North Carolina at Chapel Hill researchers report a 50 percent reduction in the number of deaths among kidney hemodialysis patients who are given a new drug that helps prevent excess phosphorus from accumulating in the bloodstream. "The drug, lanthanum carbonate, is effective. Its well-tolerated, and patients find it reasonably easy to take," said Dr. William Finn, nephrologist and professor of medicine at UNC.
Study findings will be presented Saturday (Nov. 2) at the American Society of Nephrology annual meeting in Philadelphia. More than 350,000 people in the United States receive treatment for kidney failure, or end-stage renal disease, according to the National Institutes of Health. Of these, about 60 percent undergo hemodialysis, a process that removes wastes and excess fluid from the bloodstream by passing it through a membrane in an artificial kidney machine.
Although regular hemodialysis treatment helps maintain life, studies show it provides about a tenth of the cleaning function of normal kidneys. Moreover, those on the treatment run an increased risk of cardiovascular disease and other medical problems. "One of the things hemodialysis does not do well is remove phosphorus from the blood," Finn said. "About 50 to 60 percent of patients on chronic hemodialysis do not have adequate phosphorus control; they have high phosphorus levels."
Finn added that elevated blood levels of phosphorus help trigger hyperparathyroidism, a condition that may lead to serious bone and cardiovascular problems. Some research indicates an increased risk for cardiac death possibly due to a buildup of calcium in coronary blood vessels.
Moreover, beginning in 1998, reports in medical literature have identified elevated phosphorus blood levels as independent risk factors for mortality among kidney patients on hemodialysis. The National Kidney Foundation has subsequently lowered its recommended phosphorus blood levels.
Today, many kidney failure patients undergoing hemodialysis take medications that bind dietary phosphorus, thereby allowing its excretion in the stool rather than its absorption by the body.
Originally, aluminum hydroxide or aluminum containing compounds were used "because aluminum binds phosphorus very well," Finn said. "Unfortunately, some of the aluminum was absorbed and found its way into bone and brain tissue, causing serious bone disease and a condition known as dialysis dementia."
Other phosphorus or phosphate binding agents were then used, including calcium carbonate (a main ingredient in popular stomach relievers) and calcium acetate. However, some patients using these calcium-based binders develop hypercalcemia, high calcium levels, prompting a search for other types of phosphate binders.
Recently, a non-calcium phosphate binder, Renagel, has come into use. Its maker, Genzyme Corp., sponsored a major clinical study in which hemodialysis patients taking their drug showed less coronary artery calcification than did patients taking calcium-based phosphate binders. However, differences in cardiac mortality among patients in the different drug group binders were not demonstrated in that study, Finn said. A separate study addressing this issue is under way.
The UNC investigation involves the newly developed, non-calcium phosphate binder, lanthanum carbonate (Fosrenol), developed by Shire Pharmaceuticals Group, PLC, in the United Kingdom and not yet federally approved for use in the United States.
Lanthanum is a rare earth element, a heavy metal that binds phosphorus. Results of a study of bone biopsies in the United States and Europe earlier this year found no abnormalities, Finn said.
"In addition, theres no evidence that lanthanum crosses the blood-brain barrier. Tests of cognitive function are being used to determine any central nervous system changes with Fosrenol use."
In the randomized two-year study, 647 kidney hemodialysis patients received lanthanum carbonate therapy and 642 patients received conventional phosphate binders. Patients ranged in age from 19 to 91 years. The first interim analysis indicated a reduction in mortality in the Fosrenol group, compared to those taking conventional drug therapy. A second interim analysis indicated a widening disparity with a reduction in mortality, 3.3 percent versus 5.8 percent. Moreover, fewer people died of what appear to be cardiac factors.
"I think this drug, Fosrenol, or drugs like it will become the preferred phosphate binders," Finn said.
Note: Contact Finn at 215-625-2900 between Thursday (Oct. 31) and Saturday (Nov. 2). Otherwise, contact him at 919-966-2561, ext. 226, or firstname.lastname@example.org
School of Medicine contact: Les Lang, 919-843-9687 or email@example.com
Leslie H. Lang | EurekAlert!