Intravenous calcitriol versus paricalcitol in haemodialysis patients with severe secondary hyperparathyroidism

Secondary hyperparathyroidism (SHPT) is common among haemodialysis patients. Intensive treatment with calcitriol is often complicated by hypercalcaemia, hyperphosphataemia and elevated calcium phosphorus (Ca X PO(4)) product. Paricalcitol is a vitamin D analogue developed to overcome some of the limitations of calcitriol therapy. The study objectives were to compare the response of intact parathyroid hormone (iPTH) and the incidence of hypercalcaemia, hyperphosphataemia and elevated Ca X PO(4) product in patients with severe SHPT treated with either i.v. calcitriol or i.v. paricalcitol.

This was a single centre randomized open label study. Patients with serum intact iPTH of 50 pmol/L or more were randomized to receive either i.v. calcitriol (0.01 ug/kg) or i.v. paricalcitol (0.04 ug/kg) during every haemodialysis treatment. Serum iPTH, calcium, phosphorus and alkaline phosphatase were measured at the beginning of the study and every 3 weeks for 12 weeks.

Twenty-five patients were enrolled into the study - 12 were randomized into the calcitriol group and 13 into the paricalcitol group. There were no differences in the baseline study parameters between both groups. Serum iPTH levels were significantly reduced (P = 0.003) only in the paricalcitol group but not in the calcitriol group (P = 0.101). On the other hand, serum calcium levels were significantly increased only in the calcitriol group (P = 0.004 vs P = 0.242). Serum phosphorus, alkaline phosphatase and Ca X PO(4) product were not different.

Intravenous paricalcitol may be superior to i.v. calcitriol for the treatment of severe SHPT in our chronic haemodialysis population. A larger randomized controlled trial is indicated to confirm these initial findings.