[Component composition and admixtures of related compounds in commercial preparations with an erythromycin base].

Chromatographic purity of erythromycin base preparations manufactured in the USSR with various technological procedures and those of 4 foreign firms was studied. All the preparations studied in addition to the main component of erythromycin A contained 5 to 7 per cent of erythromycin C and about 1.5 to 3.5 per cent of a non-identified component possessing a somewhat lower chromatographic mobility than erythromycin C. The admixture of 0.5--1 per cent of anhydroerythmycin was found in many erythromycin preparations. The preparations of some foreign firms contained also a number of additional substances. It was shown that the antimicrobial activity of anhydroerythromycin was 50-60 times lower than that of erythromycin. Direct correla;ion between the level of the antimicrobial activity of the market prepaetions of erythromycin and the level of its chemical purity was noted.