Intravenous calcitriol for treatment of hyperparathyroidism in children on hemodialysis

Abstract

This double-blind, placebo-controlled study evaluated the safety and efficacy of intravenous (i.v.) calcitriol (Calcijex) for treatment of secondary hyperparathyroidism (secondary HPT) in pediatric end-stage renal disease (ESRD) patients on hemodialysis (HD). After a 2 to 6-week washout period of all vitamin D compounds, patients with two consecutive PTH values > 400 pg mL(-1), calcium levels < or = 10.5 mg dL(-1) and calcium x phosphorus product values < or = 70 mg2 dL(-2) were eligible for the treatment phase. Patients received a bolus injection of calcitriol or placebo three times a week, immediately after dialysis for up to 12 weeks. Initial doses (0.5-1.5 microg) were based on the severity of secondary HPT. The dose was increased every two weeks by 0.25 microg until there was at least a 30% decrease in PTH from baseline, or Ca > 11.0 mg dL(-1), or Ca x P > 75 mg2 dL(-2). Overall, 11/21 (52%) patients in the calcitriol group had two consecutive > or = 30% decreases from baseline in serum PTH compared with 5/26 (19%) patients in the placebo group (P=0.03). The mean total alkaline phosphatase decreased from 274 to 232 IU L(-1) in the calcitriol group and increased from 547 to 669 IU L(-1) in the placebo group (P=0.002). The mean bone-specific alkaline phosphatase decreased from 72.5 to 68 microg L(-1) in the calcitriol group and increased from 105.3 to 148.5 microg L(-1) in the placebo group (P=0.03). The incidence of two consecutive occurrences of elevated calcium x phosphorus (Ca x P > 75 mg2 dL(-2)) product was higher in the calcitriol group than in the placebo group (P=0.01). Two consecutive occurrences of phosphorus > 6.5 mg dL(-1) occurred in 71% of the calcitriol group and 46% of the placebo group (P=0.14). Calcium levels > 10.5 mg dL(-1) were more common in the calcitriol group than in the placebo group (P=0.01). There was a direct relationship between serum phosphorus concentration and the percentage change in PTH from baseline in both the calcitriol group (r=0.46; P<0.0001) and the placebo group (r=0.21; P=0.0005). This study demonstrates that i.v. calcitriol, at initial doses of 0.5-1.5 microg, effectively reduces PTH levels in pediatric HD patients and that patients should be closely monitored for hyperphosphatemia and elevated Ca x P product.