Comparison of the Effects of Daily and Intermittent‐Dose Calcitriol on Serum Parathyroid Hormone and Ionized Calcium Concentrations in Normal Cats and Cats with Chronic Renal Failure

Abstract

Background: Chronic renal failure is complicated by secondary hyperparathyroidism, which traditionally has been controlled by dietary restriction of phosphorus and administration of phosphorus binders. Early treatment of patients with chronic renal failure with calcitriol may be indicated because once established, parathyroid gland hyperplasia does not readily resolve with therapy.Hypothesis: Daily and intermittent dosing of calcitriol will decrease plasma parathyroid hormone concentration in normal cats and cats with chronic renal failure without causing ionized hypercalcemia.Animals: Ten normal cats; 10 cats with chronic renal failure. Methods: Phase 1 was daily calcitriol administration (2.5 ng/kg PO q24h) for 14 days. Phase 2 was intermittent calcitriol administration (8.75 ng/kg PO q84h) for 14 days. A 7-day washout period separated phases 1 and 2. Before each phase, calcitriol, parathyroid hormone, and ionized calcium concentrations were measured. On days 1, 2, and 3 of both phases, serum ionized calcium concentrations were measured. On the last day of both phases, calcitriol, parathyroid hormone, and ionized calcium concentrations were measured 0, 2, 4, and 6 hours after calcitriol administration.Results: Overall, serum parathyroid hormone concentrations were significantly higher in cats with chronic renal failure than in normal cats (P 5 .022), but serum parathyroid hormone concentrations for both normal cats and cats with chronic renal failure were not significantly different before and after 14 days of treatment with calcitriol, regardless of whether calcitriol was administered daily or intermittently. Adverse effects of calcitriol administration (specifically ionized hypercalcemia) were not seen in either feline group during either phase of the study over the 3-day evaluation after calcitriol administration was initiated.Conclusions and Clinical Importance: At the dosages used, calcitriol treatment did not result in significant differences in serum parathyroid hormone concentrations before and after treatment in both normal cats and cats with chronic renal failure. With these dosages, adverse affects of calcitriol administration were not seen. Potential reasons for lack of apparent effect include small sample size, insufficient duration of study, insufficient dosage of calcitriol, problems with formulation or administration of calcitriol, and variable gastrointestinal absorption of calcitriol.

Urinary Calcium and Oxalate Excretion in Healthy Adult Cats Are Not Affected by Increasing Dietary Levels of Bone Meal in a Canned Diet

“…A higher provision of Ca with the diet has obviously resulted in a lower synthesis and secretion of PTH compared to the situation of a lower Ca intake with diet A. However, all values for PTH were within the normal range of 3.3–22.5 pg/ml given by the analyzing laboratory, which was nearly similar to reference data given in the literature [33].…”

Calcitriol, calcidiol, parathyroid hormone, and fibroblast growth factor‐23 interactions in chronic kidney disease

“…Ten healthy and 10 cats with CKD (mean ± SD creatinine: 249.3 ± 45.1 μmol/L [2.82 ±0.51 mg/dL]) were treated for 14 days with calcitriol 2.5 ng/kg/day and later (after 7‐day washout period) with 8.75 ng/kg every 84 hours. Even though baseline PTH differed among groups, PTH did not significantly decrease after calcitriol treatment in either group or treatment interval . Calcitriol concentration did not change regardless of treatment group or interval.…”

Serum intact parathyroid hormone levels in cats with chronic kidney disease

“…According to evidence-based medicine, administration of calcitriol has proven to be effective in the treatment of SRHPT in dogs with CKD, having scientific support for use in stages III or IV and even in the cases in which serum iPTH levels are within normal ranges (Polzin 2007, Polzin et al 2009b, Roudebush et al 2010. However, for cats with CKD in Stages III or IV, the use of calcitriol seems to have a weak scientific support, requiring further investigation (Hostutler et al 2006, Polzin et al 2009a.…”