Paricalcitol versus Calcitriol in the Treatment of Secondary Hyperparathyroidism in Hemodialysis Patients

Abstract

Purpose

A mainstay treatment of secondary hyperparathyroidism has been the administration of vitamin D analogs. Paricalcitol is a vitamin D analog thought to reduce parathyroid hormone (PTH) levels with fewer effects on calcium (Ca) and phosphorous (P) levels than intravenous calcitriol. However, there are limited data directly comparing the 2 agents. The primary objective was to compare the efficacy of paricalcitol to calcitriol in hemodialysis patients. Secondary objectives evaluated the safety and direct costs associated with these agents.

Methods

This was a retrospective study of hemodialysis patients who received at least 8 weeks of both therapies from 2002 to 2004. Primary outcomes included the percentage of patients achieving greater than or equal to 50% reduction in baseline PTH levels; the change in PTH levels from baseline to the end of therapy; and time to achieve greater than or equal to 50% reduction in baseline PTH concentrations. Secondary outcomes included the percentage of patients experiencing hypercalcemia, hyperphosphatemia, or elevated Ca and P product; and the percentage of patients hospitalized secondary to these side effects.

Results

Calcitriol-treated patients showed a median reduction in PTH concentrations from baseline to the end of treatment phase of 8.3% versus paricalcitol reduction of 1.5%. This result was not statistically significant (P = 0.08); however, it should be examined in a study powered to detect this difference. A similar number of patients in both treatment groups were able to achieve a greater than or equal to 50% reduction in baseline PTH concentrations but calcitriol-treated patients were more likely to achieve this primary end point faster than the paricalcitol-treated group (166 days vs 207 days, respectively, P = 0.18). The incidence of side effects between the agents was similar. There was a substantial difference in the annual drug cost between paricalcitol and calcitriol.

Conclusion

Paricalcitol did not seem to result in clear efficacy and safety benefit over calcitriol in this study. However, due to the study's retrospective design and potential for a type 2 error, as well as limited published data comparing this agent to calcitriol, additional research is required before paricalcitol becomes the standard of care in patients with chronic kidney disease and secondary hyperparathyroidism.