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)2D3 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 μg, second month 4 μg, third month 6 μg 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.