LETTERS TO THE EDITOR an excellent agent for skeletal imaging

The diphos phonate is a stable chemical in aqueous solutions, and there is still no evidence that it is metabolized in vivo, unlike linear polyphosphates. Despite the increasing number of publications on the pharma cology and toxicity of diphosphonates, most of these have reported results of oral or subcutaneous admin istrations, and there is still a paucity of information On intravenous toxicity. In our laboratory, the LD50130for EHDP administered intravenously as a tin complex was 45—50mg EHDP/kg body weight in albino mice and 40—45 mg/kg in New Zea land adult rabbits compared with 100 mg/kg in both mice and rabbits for linear polyphosphate. Re cent measurements of the long-term retention o