TY - JOUR T1 - METABOLISM OF PROPIONYL ERYTHROMYCIN LAURYL SULFATE JF - Drug Metabolism and Disposition JO - Drug Metab Dispos SP - 155 LP - 163 VL - 3 IS - 3 AU - PATRICK J. MURPHY AU - TERRY L. WILLIAMS AU - ROBERT E. McMAHON AU - FREDERICK J. MARSHALL Y1 - 1975/05/01 UR - http://dmd.aspetjournals.org/content/3/3/155.abstract N2 - The absorption. excretion, and metabolism of propionyl erythromycin ( PE) has been studied in the rat. The major routes of metabolism of PE are ester hydrolysis and N-demethylation. The rates of these two reactions have been examined in vivo using radiolabeled PE. The plasma half-life of the ester is 5.5 hr. The correlation of blood levels of radioactivity with 14C02 production mdicates that the ester is continually hydrolyzed after absorption. The half-life of the dimethyl-amino moiety of the desosamine sugar is estimated at 1.5 hr. This relatively short half-life compared to that of the ester is supported by the fact that at 3.5 hr after dosing there is twice as much desmethyl-PE in plasma as PE. After oral administration of either 14C-PE or 14C-erythromycin. 70% of the radioactivity is absorbed in 6 hr. The major route of excretion is via bile. Approximately 40% of the absorbed dose is excreted in bile in the first 6 hr after dosing. Tissue levels of radioactivity after administration of 14C-erythromycin or 14CPE indicate that PE or a metabolite accumulates in the tissue during chronic dosing. whereas erythromycin-related levels are similar after single or multiple doses. Copyright © 1975 by The American Society for Pharmacology and Experimental Therapeutics ER -