Modern principles of treatment involve the frequent use of antibiotics in infectious diseases. One of the most considered antibiotics is the macrolide group. It is these drugs that have relatively few side effects, while at the same time preventing the development of a significant number of dangerous microorganisms and intracellular parasites. A significant disadvantage of macrolide antibiotics is the resistance to their action by many bacteria. This article investigates the preventive effectiveness of three types of macrolide antibiotics in infectious diseases and dysbiosis in the example of laboratory animals. Observations were carried out on four similar groups of laboratory animals, which received erythromycin, azithromycin, and midecamycin as prophylactic drugs. The fourth group was a control group that did not receive any treatment. According to the results of the study, a conclusion was made about the effectiveness of the drugs used. In infectious diseases, the final effectiveness of erythromycin was 60%, azithromycin - 80%, and midecamycin - 55%. In dysbiosis, the efficacy of erythromycin and azithromycin was 100%, and of midecamycin - 90%. The use of macrolide antibiotics for preventive purposes also significantly reduced mortality rates, which in the control were 35% for infectious diseases and 10% for dysbiosis.