Abstract. The purpose is to study the influence of the hepatoprotective phytocomplex on the severity of endogenous intoxication in laboratory rats with experimental liver pathology caused by hydrazine. Methods. The studies were carried out on non-linear rats, formed into 3 groups (n = 10). Toxic damage to the liver in rats of groups 1 and 2 was modeled by a single intragastric administration of hydrazine at a dose of 200 mg/kg of body weight. Immediately after intoxication and for the next three weeks in 1st group, the drug fitosomin was used – daily orally in the form of boluses at a dose of 0.5 g/kg of body weight, 2nd group after intoxication received empty cereal boluses, 3rd group was intact. In dynamics, the degree of endogenous intoxication was studied by the concentration of medium mass molecules (MMM) in the blood of animals at λ = 254 and 280 nm. Scientific novelty. Experimentally new data on the pharmacological effects of the hepatoprotective phytocomplex was obtained, which includes lecithin, dihydroquercetin, extracts of milk thistle, agrimony and golden boletus. For the first time, the effectiveness of the drug fitosomin was determined to reduce the severity of the endogenous intoxication syndrome in laboratory rats with experimental liver pathology caused by hydrazine. Results. It has been determined that hydrazine-induced liver pathology in laboratory rats is accompanied by the development of endogenous intoxication syndrome with a more pronounced increase in the blood fraction of MMM 254 relative to MMM 280. The use of fitosomin leads to a weakening of the toxic effect of hydrazine both on the liver and on the body of animals as a whole. The course application of the hepatoprotective phytocomplex increases the survival rate of rats, improves their clinical condition and leads to a decrease in the concentration of MMM in the blood. The obtained results outlined the prospects for the use of the drug fitosomin in veterinary practice in case of liver damage, as well as intoxication of animals.