Among malignant neoplasms of women, breast cancer (BC) takes the leading place and is the cause of high mortality and complications. Side effects in the form of anemia, thrombocytopenia, bleeding, etc. often develop during cytostatic therapy, which is the main method of treatment and prevention of further development of the oncological process. In this regard, the problem of reducing side metabolic disorders remains relevant and creates a search field for the use of drugs aimed at stabilizing functions, both at the cellular and organ levels. The aim of the study was to evaluate the effect of cytostatic drugs on thrombocytopoiesis in rats with WALKER-256 carcinoma. The study included 60 rats, which, depending on the type of treatment, were divided into 5 groups. A week after the start of chemotherapy, the greatest increase in the number of platelets was in the presence of liposomal ethylmethylhydroxypyridine succinate. We recorded that the myeloprotective effect was 1/3 better in liposomal ethylmethylhydroxypyridine succinate compared to its non-liposomal form. Therefore, individuals those receiving cytostatic drugs in the treatment of breast cancer need protection from myelopoiesis. In the studies carried out by us, it was shown that oxidative stress occurred in animals against the background of treatment with cytostatics. It was its rapid development that caused damage to the platelet cell membranes. In this regard, we have proposed a drug with a pronounced antioxidant efficacy. The introduction of an antioxidant into the generally accepted standard treatment of a tumor process has made it possible to experimentally select methods for delivering the drug to the targets of damage using liposomal forms. The study obtained data proving the effectiveness of the use of liposomal ethylmethylhydroxypyridine succinate (50 mg / kg), in contrast to its free form, which prevents the development of thrombocytopenia induced by the administration of cytostatic drugs to rats with Walker-256 carcinoma.