Mixture of substances consisting of structurally very similar compounds formed by the bacterium Saccharopolyspora erythraea and used as a drug due to its antibiotic effect.
The main component of the substance mixture is erythromycin A. Other ingredients are erythromycin B (5%) and, to a much lesser extent, erythromycin C. Chemically, erythromycin can be described as a glycoside; pharmacologically, erythromycin is a macrolide antibiotic.