Chronic kidney disease-mineral and bone disorder (CKD-MBD) in dogs is associated with hypovitaminosis D, increased parathyroid hormone (PTH), and increased fibroblast growth factor-23 (FGF-23) concentrations. Best practice for vitamin D metabolite supplementation in CKD-MBD remains unknown.
To provide an extended-release calcifediol supplement to dogs with CKD and to measure its effects on variables indicative of CKD-MBD.
Ten dogs with International Renal Interest Society stages 2 and 3 CKD.
In a prospective study, dogs received a calcifediol supplement for 84 days. Serum 25-hydroxyvitamin D (25[OH]D), 1,25-dihydroxyvitamin D (1,25[OH] D), 24,25-dihydroxyvitamin D (24,25[OH] D), creatinine, calcium, phosphorus, PTH, plasma FGF-23 concentrations, and urine profiles were measured monthly during supplementation. Urine calcium to creatinine (UCa/Cr) ratios and fractional excretion of calcium, phosphorus, and sodium were determined.
All serum vitamin D metabolite concentrations increased significantly by day 84 (P < .001): [25(OH)D (median 249.9 ng/mL; range, 149.7-469.9 ng/mL) compared to baseline (median 50.2 ng/mL; range, 31.3-66.0 ng/mL); 1,25(OH) D (median 66.1 pg/mL; range, 56.9-88.1 pg/mL) compared to baseline (median 37.3 pg/mL; range, 29.3-56.7 pg/mL); 24,25(OH) D (median 81.4 ng/mL; range, 22.1-151.7 ng/mL) compared to baseline (median 15.4 ng/mL; range, 6.9-40.6 ng/mL)]. There were no significant differences in calcium, phosphorus, PTH concentrations, UCa/Cr or fractional excretion of calcium. No dog developed ionized hypercalcemia. Plasma FGF-23 concentrations increased by day 84 (median 1219 pg/mL; range, 229-8824 pg/mL) compared to baseline (median 798 pg/mL; range, 103-4.145 pg/mL) (P < .01).
Calcifediol supplementation for 84 days was well-tolerated in dogs with IRIS stages 2 and 3 CKD. It remains to be determined how long-term supplementation would affect CKD progression and QOL.

© 2020 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.