Pirlimycin in the dairy cow: metabolism and residue studies.
1992
Hornish R.E. | Arnold T.S. | Baczynskyj L. | Chester S.T. | Cox T.D. | Flook T.F. | Janose R.L. | Kloosterman D.A. | Nappier J.M. | Reeves D.R.
Pirlimycin hydrochloride (I), a lincosaminide antibiotic, is a new therapeutic agent under development for the treatment of mastitis in the dairy cow. Absorption, distribution, metabolism, excretion and residue decline studies of I have been conducted in the dairy cow following intramammary infusion of an aqueous gel formulation of I into all four quarters of the udder via the teat canals. Total milk residues accounted for only 50% of the dose and the milk residue concentration-time course was bi-phasic. Nearly half of the dose was thus absorbed for systemic circulation. Drug residue concentrations in blood were best fit to a two-compartment pharmacokinetic model. Pirlimycin accounted for greater than or equal to 95% of the drug residue in milk and was excreted predominantly as parent compound in the urine and feces. Pirlimycin sulfoxide was the major residue found in the liver, the target tissue for residue analysis. GI tract microflora converted part of the fecal drug residue to 3-(5'-ribonucleotide) adducts of pirlimycin and pirlimycin sulfoxide. The comparative metabolism of I in the rat following oral administration was nearly identical to that in the cow following intramammary infusion.
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