The effect of calcitriol, paricalcitol, and a calcimimetic on extraosseous calcifications in uremic rats.

Vitamin D derivatives and calcimimetics are used to treat secondary hyperparathyroidism in patients with chronic renal failure. We investigated the effect of calcitriol, paricalcitol, and the calcimimetic AMG 641 on soft-tissue calcification in uremic rats with secondary hyperparathyroidism. Control and uremic rats were treated with vehicle, calcitriol, paricalcitol, AMG 641, or a combination of AMG 641 plus calcitriol or paricalcitol. Parathyroid hormone levels were reduced by all treatments but were better controlled by the combination of paricalcitol and AMG 641. The calcimimetic alone did not induce extraosseous calcification but co-administration of AMG 641 reduced soft-tissue calcification and aortic mineralization in both calcitriol- and paricalcitol-treated rats. Survival was significantly reduced in rats treated with calcitriol and this mortality was attenuated by co-treatment with AMG 641. Our study shows that extraskeletal calcification was present in animals treated with calcitriol and paricalcitol but not with AMG 641. When used in combination with paricalcitol, AMG 641 provided excellent control of secondary hyperparathyroidism and prevented mortality associated with the use of vitamin D derivatives without causing tissue calcification.