Acute Toxicity of Milbemycin Oxime in Mice

Milbemycin oxime, isolated from the fermentation of Streptomyces hygroscopicus var. aureolacrimosus, is effective to parasites such as heartworm larvae, adult hookworm and mites. Kunming mice were selected for the acute toxicity study. The animals exposed to milbemycin oxime by single intragastric administration. The pretest showed that gender had effect on the LD50 value. Therefore, 70 male mice were divided into 7 groups at random, each group was given different concentration of milbemycin oxime, so did for the female mice. Each animal was observed for signs of toxicity and behavioral changes at 1 and 3h after test article administration and once daily thereafter for 14 days. Mortality/moribundity checks were performed daily. The LD₅₀ values for milbemycin oxime in male and female mice were 1 832 and 727 mg/kg, respectively, and the 95% confidence interval were 1 637.57~2 022.08 mg/kg and 603.95~868.96 mg/kg, respectively.