Effects of intravenous and oral OCT on secondary hyperparathyroidism in dogs with chronic renal failure

Abstract

In this study, we compare the relative potency of single intravenous OCT (IV OCT) and 1,25 (OH) (2)D(3) [IV 1,25 (OH) (2)D(3)] on serum PTH and ionized calcium (ICa) in dogs with chronic renal failure (CRF). In addition, we examine the efficacy of intermittent IV OCT. A single dose of OCT (5 microg/kg) to uremic dogs suppressed PTH by 81% without a statistical significant change in serum I Ca. On the other hand, any of the effective doses of 1,25 (OH) (2)D(3) on PTH suppression were hypercalcemic. The intermittent administration of OCT (0.1 microg/kg) or 1,25 (OH) (2)D(3) (0.025 microg/kg), 3 times per week IV suppressed serum PTH by 83% or 77%, relatively without hypercalcemia. To evaluate OCT as an oral drag, it was given intermittently (3 times per week) to a group of 6 uremic dogs for a period of 4 weeks. Subsequently it was changed to a daily administration (0.05 microg/kg) for a period of 2 weeks. Finally the dose was reducted to 0.025 microg/kg. Daily OCT 0.05 microg/kg suppressed serum PTH by 67%. Subsequently 0.025 micro/kg maintained serum PTH within the normal range without hypercalcemia for 4 weeks. OCT seems to be promising as a useful agent not only for hemodialysis patients but also for predialysis and CAPD patients. In conclusion, our results suggest that OCT is a useful vitamin D(3) analogue, which has a potentially larger therapeutic window than that of 1,25 (OH) (2)D(3) and which is available for IV/oral, for the management of secondary hyperparathyroidism.