Effects of Lanthanum Carbonate on Whole-Body Phosphorus and Calcium Balance in Adults With Chronic Kidney Disease and Normophosphatemia

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Rationale & Objective Greater serum phosphorus is associated with cardiovascular disease (CVD) in those with chronic kidney disease (CKD). However, the utility of phosphorus lowering in non-dialysis requiring CKD is not clear. The effects of non-calcium-phosphate binders on phosphorus and calcium balance in non-dialysis requiring CKD are unknown. Our objective was to determine phosphorus and calcium balance in normophosphatemic adults with CKD 3b-4 after 12 weeks of treatment with lanthanum carbonate or placebo. Study Design Prospective, randomized, controlled, double-blind clinical trial. Setting & Participants A subset of 15 adults with CKD 3b-4 and serum phosphorus within normal limits who participated in a 12-week parallel-arm, randomized controlled trial of lanthanum carbonate compared with placebo on vascular function participated in this study extension. Intervention At the end of 12 weeks, the subset of participants consumed a controlled diet (1000 mg/day phosphorus and 800 mg/day calcium) for 9 days and continued their randomly assigned study drug (N=7 lanthanum carbonate, N=8 placebo). Fasting morning blood samples and all stool and urine were collected during a 48-hour inpatient clinical research center stay at the end of the 9-day controlled diet period. Outcomes Phosphorus and calcium balance (mg/d) were determined by values averaged over the 48 hours inpatient clinical research center admission. Results Mean age was 65±8 (SD) years and mean eGFR was 38±14 (SD) mL/min/1.73m 2 . Whole-body phosphorus balance was lower with lanthanum carbonate compared with placebo [-131±163 (SEM) vs. 320±141 mg/d, p=0.05], as was calcium balance [-46±115 (SEM) vs. 410±100 mg/d, p=0.01], corresponding to lower intestinal absorption supported by the fecal calcium and phosphorus and net absorption results. Neither 24-hour urine calcium nor phosphorus was significantly different between lanthanum carbonate and placebo, but 24-hour urine phosphorus differed between lanthanum carbonate and placebo but was not significant (388±60 v. 513±56 mg/d, p=0.15). Limitations Small sample size. Conclusions 12 weeks of treatment with the non-calcium-based phosphate binder, lanthanum carbonate, may reduce whole-body phosphorus balance as well as calcium balance among adults with stage 3b-4 CKD and normophosphatemia. Whether reduced phosphorus balance or calcium balance with lanthanum carbonate is associated with beneficial clinical outcomes in CKD warrants further investigation.

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