Avermectines are new class of antibiotics with acaricidal and anthelmintic activity. New medicine containing macrocyclic lactones is Eprimec. One milliliter of Eprimec contains 10mg of eprinomectin as active substance. The aim of our study was to determine the extent of karyopatic and cytotoxic effects of that preparation to cell division process in testes of white mice. The materials for the study were the non-linear white mice -males 18 -22 g. Experimental group of mice received a dose of 200 micrograms of active compound per 1 kg of weight or 10 mg / ml of eprinomectin by single subcutaneous injection. The control group of animals remained intact. Each group consisted of 8 mice. The animals were slaughtered at 12 hours after drug administration. Testes of mice were isolated, smears -imprints were prepared that are fixed by May -Grunewald and stained with azure -eosin by Romanovsky. Glass slides with testes cells were viewed under a microscope and implemented to count the number of dividing cells, take into account the shape, size and color of the nuclei. Analysis of the frequency of occurrence of a karyopatic disorders and cytotoxic effects of cells were performed separately and lying sprawled cells with counting at least 1000 cells in each glass slide (Lazareva et al, 2016). Analyzing the data, we concluded that on the basis of eprinomectin formulations significantly reduce the activity of cell division, but it is toxic and cause serious karyopatic changes in the cells of the testes nonlinear white mice, indicating that the negative effects on the reproductive system of males.