Safety and Efficacy of Long-Term Treatment of Secondary Hyperparathyroidism by Low-Dose Intravenous Calcitriol

Abstract To assess the safety and efficacy of low-dose intravenous (IV) calcitriol therapy for the treatment of secondary hyperparathyroidism, 21 hemodialysis patients with amino-terminal parathyroid hormone (N-PTH) levels greater than 4 times normal were treated for 12 to 24 months in a prospective trial. The initial dose was 0.50 δg, which was titrated every 3 months thereafter, as dictated by predialysis calcium, phosphorus, and N-PTH concentration. Dialysate calcium concentration was 1.5 mmol/L. Low-dose IV calcitriol decreased the N-PTH concentration to 48 ± 6% and 29 ± 5% of baseline following 12 and 24 months of therapy, respectively. The maximum dose of calcitriol was 0.92 ± 0.11 δg (0.50 to 2.25 δg). After 12 months of therapy, serum calcium increased from 2.22 ± 0.04 to 2.41 ± 0.03 mmol/L (8.9 ± 0.2 to 9.7 ± 0.1 mg/dL) without change thereafter. Baseline serum phosphorus was 1.44 ± 0.09 mmol/L (4.5 ± 0.3 mg/dL), and was unaltered by calcitriol therapy. Control of serum phosphorus was achieved with calcium-containing phosphate binders, except in three patients who were subsequently withdrawn from the study after 12 months because of persistent hyperphosphatemia due to noncompliance. We conclude that long-term, low-dose IV calcitriol is a safe and effective therapy for most hemodialysis patients with secondary hyperparathyroidism. In contrast to conventional dosing regimens, low-dose IV therapy does not necessitate the use of aluminum-containing phosphate binders and/or a low-calcium dialysate bath.