Fosrenol and Phosphorus Balance - Lanthanum Carbonate

Seven clinically stable patients who have been undergoing CPD for at least six months will be admitted to the General Clinical and Research Center (GCRC) at Harbor-UCLA Medical Center for 46 days. During this time they will be fed, under strict metabolic balance study conditions, a constant energy and protein intake designed to meet their previously ascertained nutritional needs. Their dietary intakes of phosphorus, calcium and magnesium will be maintained constant throughout the 46 days of study at 1100 mg/day, 1000 mg/day and 200 mg/day, respectively. Patients will be treated throughout the study with a constant peritoneal dialysis regimen that consists of either continuous ambulatory peritoneal dialysis with four dialysate exchanges daily or automated peritoneal dialysis in which they will each receive about four dialysate exchanges per night; and possibly day-time dialysate exchanges. The number and volume of dialysate exchanges and the dialysate glucose concentration may vary among patients according to their metabolic and clinical needs, but will be constant for each patient. Patients will adhere to standard metabolic balance protocols as the investigators have conducted during our many previous metabolic balance studies. These protocols will include participating in prescribed daily exercise regimens that are designed to maintain the patients' physical activity at their prestudy, outpatient levels. All patients will first undergo a 10 day Baseline period for metabolic equilibration during which time they will not receive any phosphate binder. They will then receive three periods of Fosrenol treatment with three different dose levels for 12 days each. During each of three periods, the patients will receive, in random order, one or two Fosrenol tablets that will provide 500, 1000, or 1500 mg with each of the three meals that they will be fed each day. Thus these CPD patients will receive in random order 1500, 3000 and 4500 mg/day of Fosrenol each prescribed for one 12 day period. Outcome Measurements. All urine, collected in 24 hour urine specimens, and all feces excreted, collected over four day periods, will be obtained continuously. Every 4 days a duplicate 24 hour diet will be prepared for chemical analyses. The above specimens will be analyzed for phosphorus, calcium and nitrogen by spectrographic, atomic absorption spectroscopic and Kjeldahl analyses, respectively. Serum phosphorus, calcium, parathyroid hormone (PTH), fibroblast growth factor-23, 25-hydroxycholecalciferol (25(OH)D3), 1,25-dihydroxycholecalciferol (1,25(OH)2D3), fetuin-A, urea and creatinine will be measured in the fasting state at the beginning of the 40 day balance period and every 5 days. Anthropometry and other standard measurements that are routinely conducted during metabolic balance procedures will also be performed.