THE EXCRETORY PRODUCTS OF N-METHYL-C¹⁴-ERYTHROMYCIN IN RATS

¹ The Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana

The excretory products of erythromycin were studied in ten rats following intravenous administration of X-methyl-C¹⁴-erythromycin.

The original injected erythromycin accounted for about one-half to four-fifths of the total radioactivity excreted in the urine; one-half in the bile; and one-third in the feces.

The only microbiologically active metabolite of erythromycin was des-N-methyl-erythromycin. It was excreted in the bile and passed out through the feces.

Des-N-methyl-erythromycin resulted from N-demethylation of the parent antibiotic by the liver. This metabolite accounted for about one-third of the total bile radioactivity during the two-hour period following isotopic erythromycin administration.

Seven additional metabolites of erythromycin were not identified. Two of these were excreted in the bile; three in the urine; and two in the feces. The latter two may be produced from metabolism of erythromycin by intestinal bacteria.