Twice versus thrice weekly administration of intravenous calcitriol in dialysis patients: a randomized prospective trial

Background: Administration of intravenous (i.v.) calcitriol three times weekly effectively controls the synthesis and secretion of PTH in most uremic patients. Administration of a single dose of 1.25(OH)(2)D-3 reduces synthesis of PTH-mRNA for 6 days in rats. Moreover, it can lower PTH levels for up to 4 days in chronic hemodialysis patients. Therefore, a good response to the administration of i.v. calcitriol two times weekly can be expected. We studied - in a multicenter randomized study in patients with moderate to severe secondary hyperparathyroidism - the effects of the same doses of intravenous calcitriol, administered two or three times weekly. Methods: Twenty-two hemodialysis patients were randomized into two frequencies of treatment groups: two times (G-2/w) and three times weekly (G-3/w). Both groups were treated with increasing doses of intravenous calcitriol for 3 months (first month 3 mu g, second month 4 Gig, third month 6 mu g weekly). Results: After 12 weeks of therapy with intravenous calcitriol the G-2/w group showed a significant reduction in serum PTH levels (from 821 +/- 392 to 350 +/- 246 pg/ml; mean reduction = 57.4%) comparable to the decrease observed in the G-3/w group (from 632 +/- 116 to 246 +/- 190 pg/ml; mean reduction = 61.2%). Ionized calcium (G-2/w from 1.13 +/- 0.10 to 1.14 +/- 0.08 and G-3/w 1.21 +/- 0.13 to 1.26 +/- 0.18 mmol/l) and phosphate levels (G-2/w from 4.99 +/- 1.01 to 5.99 +/- 1.78 and G-3/w 5.31 +/- 0.73 to 5.81 +/- 1.18 mg/dl) did not change significantly and phosphate binders were not modified during the study. Conclusion: This study confirms that intravenous calcitriol is an effective therapy for moderate to severe secondary hyperparathyroidism. The administration of two doses per week of intravenous calcitriol is as efficacious as three doses per week in suppressing PTH secretion.