Doxercalciferol safely suppresses PTH levels in patients with secondary hyperparathyroidism associated with chronic kidney disease stages 3 and 4.

BACKGROUND: Calcitriol lowers parathyroid hormone (PTH) levels in patients with chronic kidney disease (CKD) stages 3 and 4, but its use is limited by a low therapeutic index and concerns regarding hypercalcemia and acceleration of kidney disease. We evaluated doxercalciferol (1alpha-hydroxyvitamin D2) as an alternative therapy in a randomized, double-blinded, placebo-controlled, multicenter trial. METHODS: Fifty-five adults with stage 3 or 4 CKD and an intact PTH (iPTH) level greater than 85 pg/mL (ng/L) completed 8 baseline weeks, followed by 24 weeks of oral therapy with doxercalciferol or placebo. Pretreatment demographics and biochemical features did not differ between groups. Dosages were increased gradually if iPTH level was not decreased by 30% or greater and serum calcium and phosphorus levels were stable. Regular monitoring included plasma iPTH, serum calcium and phosphorus, urinary calcium, bone-specific serum markers, and serum lalpha,25-dihydroxyvitamin D levels. Glomerular filtration rate (GFR) was measured before and after treatment. RESULTS: Mean plasma iPTH level decreased by 46% from baseline after 24 weeks of doxercalciferol treatment (P <0.001), but was unchanged with placebo. After 6 weeks, iPTH level reductions with doxercalciferol treatment exceeded those with placebo at all subsequent intervals (P <0.001). No clinically significant differences in mean serum calcium or phosphorus or urinary calcium levels or incidence of hypercalcemia, hyperphosphatemia, or hypercalciuria were noted between groups. Serum C- and N-telopeptide and bone-specific alkaline phosphatase levels decreased with doxercalciferol treatment relative to both baseline and placebo (P <0.01). Adverse-event rates and changes in GFR did not differ between groups. CONCLUSION: Doxercalciferol is safe and effective in controlling secondary hyperparathyroidism of patients with CKD stages 3 and 4.

Use of active vitamin D sterols in patients with chronic kidney disease, stages 3 and 4.

This paper reviews randomized controlled trials and other reported data on the use of the active vitamin D sterols, such as calcitriol, alfacalcidol, and doxercalciferol, in the management of secondary hyperparathyroidism in patients with mild-to-moderate renal insufficiency (stage 3 or 4 chronic kidney disease). Data on potential benefits, including improved histologic abnormalities of bone from secondary hyperparathyroidism, increased bone mineral density, and a reduction of elevated parathyroid hormone levels, are documented. Consideration is given to the risks of such therapy, which include the production of hypercalcemia, more rapid progression of renal insufficiency, the induction of adynamic bone "disease," and accelerated vascular and soft tissue calcification. The low therapeutic index, or "benefit/risk ratio" of calcitriol and alfacalcidol, the sterols currently licensed for such treatment, is recognized. It is recommended that phosphate-restricted diets, phosphate-binding agents, and oral calcium supplements be given adequate trials before starting calcitriol or alfacalcidol. If PTH levels cannot be controlled by these measures, initial doses of these sterols and the proper surveillance during treatment are given. It is emphasized that the risks of hypercalcemia are likely to increase as the degree of kidney failure worsens. Further research using the "less calcemic" vitamin D sterols is clearly needed.