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| |  Cinacalcet Balances Calcium, Parathyroid Hormone Levels in Dialysis Patients With ESRD WASHINGTON, DC -- July 15, 2008 -- Cinacalcet not only lowers calcium and parathyroid hormone (PTH) levels in patients receiving dialysis for end-stage renal disease (ESRD), but it changes, or resets, the balance between calcium and PTH levels in the long term, according to a study in the November issue of Journal of the American Society of Nephrology. "In haemodialysis patients, the use of calcimimetics decreases the set point of the PTH-calcium curve, which means that PTH secretion by cells is suppressed at low or normal calcium levels," said Mariano Rodriguez, MD, Nephrology Service, Hospital Universitario Reina Sofia, Cordoba, Spain. Dr. Rodriguez and colleagues studied responses to cinacalcet treatment in 9 patients with ESRD receiving long-term haemodialysis to replace lost kidney function. All patients had high levels of PTH. The researchers assessed the PTH-calcium curve by comparing blood samples obtained during dialysis performed at low and high calcium levels. The study took advantage of a new test that provides more complete information on the dynamics of PTH secretion. Treatment with cinacalcet led to significant reductions in the patients' blood phosphorus levels. Their levels of PTH before dialysis were also decreased. Cinacalcet also led to a reduction in the set point of the PTH-calcium curve. The study provides important new information on how cinacalcet and other calcimimetic drugs work to reduce PTH levels. Normally, low calcium levels cause cells to increase secretion of PTH. After cinacalcet treatment, PTH secretion doesn't increase even when calcium levels are low. "Nowadays the calcimimetics are an essential tool in the treatment of secondary hyperparathyroidism," said Dr. Rodriguez. "With these drugs, the need for surgery to remove the parathyroid gland is markedly decreased." The results provide nephrologists with new insights into the way cinacalcet works to control PTH levels in ESRD patients with hyperparathyroidism. "High PTH levels and the excess of calcium in blood are easy to control with calcimimetics," said Dr. Rodriguez. The study was limited by the lack of data on the effects of cinacalcet in patients on peritoneal dialysis, although there are no reasons to believe that results would have been different in peritoneal dialysis patients. In addition, the patients in the study were not taking vitamin D, another effective treatment for hyperparathyroidism. "It would have been interesting to evaluate the combined effect of calcimimetics and vitamin D on the set point of the PTH-calcium curve," said Dr. Rodriguez.
SOURCE: American Society of Nephrology
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