Effects of Paricalcitol on Renal Secondary Hyperparathyroidism and Proteinuria in Dogs With Chronic Kidney Disease

Background: Renal secondary hyperparathyroidism (RHPT) is an inevitable consequence of chronic kidney disease (CKD). Paricalcitol might safely attenuate RHPT and proteinuria. Hypothesis/Objective: Paricalcitol decreases parathyroid hormone (PTH) and proteinuria in dogs with CKD. Animals: Thirteen dogs with naturally acquired CKD. Methods: Placebo-controlled clinical trial. Dogs were randomly allocated to receive a placebo or paricalcitol (14 ng/kg/day) in a crossover design of 2, 12-week arms. Dogs were evaluated every 3 weeks. Associations between treatment, visit, and the outcome variables were assessed using generalized estimating equations. Results: PTH decreased by 22% (95% CI, 7%–35%, p = 0.006) in the paricalcitol-treated dogs and increased by 18% (95% CI, 2%–37%, p = 0.022) in the placebo-treated dogs with each visit. FGF-23 at 12 weeks increased compared with baseline in the paricalcitol-treated (mean 6941 pg/mL, 95% CI, 1781–20 057 vs. 489 pg/mL, 95% CI, 188–1272, p < 0.001, respectively), but not in the placebo-treated dogs (696 pg/mL, 95% CI, 316–1531 vs. 955 pg/mL, 95% CI, 308–2963, p = 0.529). Urine protein-to-creatinine ratio at 12 weeks increased compared with baseline in the placebo-treated (0.8, 95% CI, 0.3–1.3 vs. 0.5, 95% CI, 0.2–0.9, p = 0.04, respectively), but not in the paricalcitol-treated dogs (0.6, 95% CI, 0.3–0.9 vs. 1.0, 95% CI, 0.1–1.8, p = 0.35). Ionized calcium was unchanged between baseline and 12 weeks in the paricalcitol- and placebo-treated groups (1.3 mmol/L, 95% CI, 1.29–1.35 and 1.34, 95% CI, 1.27–1.40 vs. 1.30, 95% CI, 1.25–1.35, p = 0.12 and 1.28, 95% CI, 1.24–1.32, p = 0.034, respectively). However, 7/13 dogs developed mild hypercalcemia. Adverse effects were not reported by the owners. Conclusion and Clinical Importance: Paricalcitol attenuated RHPT and stabilized renal proteinuria in dogs with CKD.