Clinical uses of 22-oxacalcitriol.

22-oxacalcitriol (OCT) is a vitamin D3 analog and a vitamin D receptor activator (VDRA) that is used as a drug for secondary hyperparathyroidism (SHPT) and has been available clinically in Japan since 2000. The pharmacological characteristics of OCT include rapid clearance from the systemic circulation compared to that of calcitriol, good tissue distribution, and relatively long retention in the nucleus in parathyroid cells. In clinical studies, OCT has been shown to decrease the parathyroid hormone (PTH) level with an effect equivalent to that of calcitriol. Other reports show that OCT produces superior improvement of bone metabolism compared to calcitriol. Treatment with ultrasound-guided direct injection of OCT into the parathyroid has also been attempted. In animal studies, OCT does not influence the blood Ca or P level and is less likely to promote progression of calcification in cardiovascular tissue. The influence of VDRAs including OCT on the progression of cardiovascular lesions and survival in SHPT patients requires further studies.