Use of pamidronate to reverse vitamin D3-induced toxicosis in dogs.

Objectives: To determine whether pamidronate disodium can reduce vitamin D3-induced hypercalcemia in dogs and whether combination treatment with calcitonin is more effective than treatment with pamidronate alone.

Animals: 20 clinically normal male Beagles.

Procedure: All dogs were given 8 mg of cholecalciferol (CCF)/kg of body weight once orally, then were assigned randomly to 4 groups of 5 dogs each. Dogs were given 0.9% NaCl solution IV (group 1), calcitonin SC and 0.9% NaCl solution IV (group 2), pamidronate and 0.9% NaCl solution IV (group 3), or a combination of all 3 agents (group 4). Dogs were observed for 28 days, and serial blood and urine samples were collected for determination of serum biochemical, electrolyte, and 25(OH)D3 values, CBC, and urine mineral excretion. Samples of kidney, stomach, lung, aorta, liver, duodenum, and brain were evaluated by light microscopy and quantitative mineral analysis.

Results: Two dogs in group 1 were euthanatized 4 days after CCF administration because of severe clinical signs of disease. Dogs in group 3 lost less weight and had significantly lower serum phosphorus, total and ionized calcium, and urinary zinc concentrations, compared with dogs in group 1. On day 4, serum urea nitrogen concentration was significantly lower in dogs of groups 3 and 4, compared with dogs in group 1. Mild to moderate mineralization of kidneys and stomach were observed in the 2 group-1 dogs euthanatized on day 4.

Conclusions: Pamidronate administration effectively prevents CCF-induced hypercalcemia and mineralization of soft tissues.

Clinical Relevance: Pamidronate is a potentially useful antidote against CCF toxicosis in dogs.