The study of immunomodulating, antioxidant and hepatoprotective activity of some fluoroquinolones (norfloxacin, ofloxacin, levofloxacin) immobilized into erythrocyte and leukocyte carriers was made on Wistar rats with body mass about 150-180 g. It is shown that toxic action on the kidneys of mercury dichloride, especially a combined action of mercury dichloride and staphylococcal infection, raised the levels of urea and creatinine, caused immunosuppression, activated hepatotoxic, cytolytic and oxidative processes, decreased antioxidant and energetic potentials of erythrocytes. Unbound fluoroquinolones intensified the above processes. Introduction of fluoroquinolones immobilized into erythrocyte and leukocyte carriers, respectively, decreased and normalized intensity of lipid peroxidation, cholestasis, cytolysis, improved and normalized immune system functions, antioxidant and energetic potentials of erythrocytes.