Comparative Toxicity of Stable Rare Earth Compounds

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Abstract
Stable rare earthchlorides, citrate, and edetate com-plexes were injected into a total of 135 anesthetized dogs. All rare earths, except promethium, were included. Yttrium was also included in the series. An amount of 100 mg/kg doses were administered intravenously as 5% solutions, in 10 mg/kg increments at 10-minute intervals. Observations were made on heart rate, blood pressure, and respiration. Blood samples were taken preanesthetically, and at 0, 10, 30, 60, 100, and 160 minutes for RBC, WBC, and differential counts, hemoglobin, hematocrit, sedimentation rate, prothrombin time, and coagulation time. No distinctive physiological response was found with any of the rare earths. Specific effects on blood constituents were an increase in prothrombin and coagulation times. The other constituents were not specifically affected by the rare earths. The chlorides were most toxic and the edetate complexes the least. Acute toxicity was of a low order; however, latent symptoms and pathology were found in single injection preliminary studies. There also was a gradation of decreasing effects from the lower to the higher members of the atomic series. Gross and histopathological examinations were essentially negative.