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

Background: Administration of intravenous (i.v.) calcitriol three times wee kly 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 synthes is 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 se vere secondary hyperparathyroidism - the effects of the same doses of intra venous 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 (firs t month 3 mu g, second month 4 Gig, third month 6 mu g weekly). Results: Af ter 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 +/- 24 6 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 1.2 1 +/- 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) di d not change significantly and phosphate binders were not modified during t he study. Conclusion: This study confirms that intravenous calcitriol is an effective therapy for moderate to severe secondary hyperparathyroidism. Th e administration of two doses per week of intravenous calcitriol is as effi cacious as three doses per week in suppressing PTH secretion.