Oral calcitriol versus oral alfacalcidol for the treatment of secondary hyperparathyroidism in patients receiving hemodialysis: a randomized, crossover trial.

BACKGROUND

Secondary hyperparathyroidism is a common complication in patients with chronic kidney disease and treatment with vitamin D analogues is a mainstay of therapy. Although oral calcitriol and alfacalcidol are used extensively in Canada, there is little published data comparing equal doses of these agents.

OBJECTIVES

To compare the effect of equal doses of oral calcitriol and alfacalcidol on intact parathyroid hormone concentrations (iPTH) in the treatment of secondary hyperparathyroidism due to chronic kidney disease. Secondary endpoints included serum 1,25-dihydroxyvitamin D3, calcium and phosphate concentrations, achievement of target iPTH concentrations, and need for phosphate binder dose increases.

METHODS

Five adult hemodialysis subjects who were naA ve to vitamin D analogues and had iPTH concentrations > or = 20 pmol/L were enrolled in a prospective, randomized 16-week crossover pilot study. Subjects were randomized to either oral calcitriol or oral alfacalcidol 0.75 mcg three times weekly for six weeks. After a four-week washout period, patients were crossed over to the alternate drug for six weeks.

RESULTS

Oral calcitriol significantly suppressed iPTH after six weeks of therapy (p=0.003), while no significant change in iPTH was observed with oral alfacalcidol.

CONCLUSIONS

This small randomized crossover study provides preliminary evidence that equal doses of oral alfacalcidol and calcitriol may demonstrate differences in iPTH suppression during the first six weeks in dialysis patients treated for secondary hyperparathyroidism. Further comparative trials are required to confirm this finding and to determine whether important differences in parathyroid hormone suppression exist between oral calcitriol and alfacalcidol beyond the six-week period. Key words: Vitamin D analogues, alfacalcidol, calcitriol, secondary hyperparathyroidism, renal dialysis.