AIM

Calcitriol and alfacalcidol are used extensively for the treatment of secondary hyperparathyroidism. Unfortunately, there is limited published data comparing the efficacy and tolerability of both active vitamin D sterols. This study was undertaken to determine whether calcitriol provides a therapeutic advantage to alfacalcidol.

METHODS

This was a randomized, active controlled study. Patients with intact parathyroid hormone (iPTH) >32 pmol/L were randomized to receive orally calcitriol or alfacalcidol after each haemodialysis for up to 24 weeks. Reduction of PTH, changes of plasma albumin-corrected calcium and phosphorus were analysed. The initial dose of alfacalcidol was twice that of calcitriol.

RESULTS

Sixteen patients were randomized into each group. At baseline, plasma albumin-corrected calcium, phosphorus and PTH were no different between groups. At 24 weeks, PTH changes were -50.8 ± 31.8% and -49.4 ± 32.5% from the baseline in the calcitriol and alfacalcidol groups, respectively (P = 0.91). The patients who achieved target PTH of 16-32 pmol/L were 82% in the calcitriol and 67% in the alfacalcidol group (P = 0.44). Plasma albumin-corrected calcium and phosphorus were not significantly different but showed trends toward gradually increasing from baseline in both groups (calcium, 6.0 ± 7.2% vs 10.9 ± 6.5% (P = 0.10); phosphorus, 13.0 ± 29.4% vs 16.7 ± 57.2% (P = 0.83) in calcitriol and alfacalcidol, respectively). The mean dose of calcitriol and alfacalcidol were 4.1 and 6.9 µg/week, respectively (P < 0.0001).

CONCLUSION

Alfacalcidol can be used to control secondary hyperparathyroidism at doses of 1.5-2.0 times that of calcitriol. The two drugs are equally efficacious and lead to similar changes in calcium and phosphorus.