Effect of oral calcidiol treatment on its serum levels and peritoneal losses.

Objectives: To evaluate calcidiol serum levels in a group of continuous ambulatory peritoneal dialysis (CAPD) patients and the effect of oral calcidiol treatment on serum levels and peritoneal losses.

Study Design: Twenty patients (13 female, 7 male) were studied for 12-60 months. Their ages ranged 22-72 years (mean 46 +/- 15). Serum calcidiol, total protein and urea were determined at baseline and after the administration per os of 0.133 mcg/day of calcidiol for 10 days. At the same time, calcidiol and total protein were measured in peritoneal effluent at baseline and at 5, 10, and 40 days after starting this treatment.

Results: A significant and direct correlation between the calcidiol dialysis/plasma ratio and the peritoneal protein losses was found, both before and 40 days after calcidiol administration when calcidiol serum levels were the lowest. As calcidiol serum levels rose to the normal range in the course of the study, peritoneal losses of this metabolite increased slightly and correlated with calcidiol serum levels and urea mass transfer coefficient (MTC); the significant correlation between calcidiol serum levels and peritoneal protein losses disappeared.

Conclusions: When serum calcidiol levels are low, calcidiol peritoneal losses in patients on CAPD correlate with protein peritoneal losses. However, when serum calcidiol levels rise, the calcidiol peritoneal losses correlate with calcidiol serum levels and urea MTC, and not with protein peritoneal losses.