[Interactions between antibiotics (author's transl)].

Combined antibiotic therapy has been used frequently to obtain broader antibacterial spectrum because of increased antibiotic resistance in microorganisms. However, antibiotics should not be combined for purposes of synergy except in certain serious infections or in infections which cannot be treated with a single drug. Other than antagonism, potential deleterious effects of combined therapy such as broader suppression of normal bacterial flora, greater risk of secondary infections and increased adverse reactions may occur during the treatment. The results of in vivo and in vitro studies in the use of combinations may be different and sometimes good clinical results can be observed with a combined therapy which is antagonistic in vitro. But, this antagonistic interaction will no be sufficient. Therefore, at the beginning of the antibiotic therapy pathogenicity of the infectious agent, defence mechanisms of the patient and the type of interaction between antibiotics must be carefully considered.