Figure 22. Effect of oral calcium vs. sevelamer on serum intact PTH (iPTH) in CKD. In this 54-week, randomized, open-label study the effects of sevelamer hydrochloride on bone structure and various biochemical parameters were compared to that of calcium carbonate in 119 patients on long-term hemodialysis therapy. Serum iPTH was consistently lower with calcium carbonate than with sevelamer treatment.