Effect of a single injection of two new bisphosphonates on the hypercalcemia and hypercalciuria induced by Walker carcinosarcoma 256/B in thyroparathyroidectomized rats.

The effect of one single injection of two new bisphosphonates, 4-amino-1-hydroxybutylidene-1,1-bisphosphonate and 2-(2-pyridyl)ethylidene-1,1-bisphosphonate, and of dichloromethylenebisphosphonate on the hypercalcemia and hypercalciuria induced by the Walker carcinosarcoma 256/B in the thyroparathyroidectomized rat was evaluated. When given either before or after the development of hypercalcemia and hypercalciuria, 16.1 mumol/kg 4-amino-1-hydroxybutylidene-1,1-bisphosphonate or 2-(2-pyridyl)ethylidene-1,1-bisphosphonate totally inhibited hypercalciuria, whereas hypercalcemia was only partially reduced over the 14 days of the experiment. At 10 and 100 times lower doses, the effect was strongest the first days, but still partially present 14 days later. The difference of activity on calcemia and calciuria appears to be due to the fact that the tumor increased both bone resorption and renal reabsorption of calcium. Only the former was altered by the bisphosphonates. The two new compounds appeared to be of similar potency and more active than dichloromethylenebisphosphonate. These compounds could be promising for the treatment of malignant hypercalcemia and other conditions with increased bone resorption in humans, even when given only over short periods of time.