Long-term effect of 1,25-dihydroxy-22-oxavitamin D(3) on secondary hyperparathyroidism in haemodialysis patients. One-year administration study.

A trial on the long-term administration of 1,25-dihydroxy-22-oxavitamin D(3) (22-oxacalcitoriol, OCT) was conducted among 124 patients with chronic renal failure on maintenance haemodialysis (HD) complicated with secondary hyperparathyroidism (2HPT). In the trial, OCT was administered three times weekly for 26 weeks subsequent to a 26-week pre-trial. As a result, intact-parathyroid hormone (PTH) levels fell significantly after the start of administration and, at the end of the trial, PTH was decreased by over 30% in 51.6% (64/124) of the patients, and the levels of bone metabolism markers such as alkaline phosphatase (ALP), bone ALP, and tartrate-resistant acid phosphatase (TRACP) were significantly decreased compared with those at the start of administration, suggesting a correction of high-turnover bone disease. Serum calcium (Ca) levels rose significantly following OCT administration, but were successfully maintained within a physiological level. Hypercalcaemia, which was diagnosed in 33.1% of patients, was found to resolve or ameliorate immediately after the withdrawal or dose reduction of OCT. OCT can be administered for as long as 1 year without any major problems other than hypercalcaemia. The final doses ranged from 2.5 to 20.0 microg/HD, and the optimal dose varied among patients depending on the intact-PTH and adjusted serum Ca levels. These results suggest that OCT is a highly effective drug for the suppression of PTH levels in 2HPT, and is an overall safe drug if the dosage is adjusted for serum Ca and intact-PTH levels. This study confirmed that the long-term (1-year) administration of OCT is very useful for the treatment of 2HPT.