title: Effect of stage of oestrous cycle on tylosin disposition in genital tract secretions of cows.
abstract: The influence of physiological state (oestrous or luteal phase) on tylosin disposition in genital secretions was examined after intravenous administration of tylosin to cows. Six healthy, cyclic and non-lactating dairy cows with controlled oestrous cycles were given a single slow intravenous injection of tylosin, at a dose of 10 mg kg-1. Plasma and genital fluid were regularly sampled up to 48 hours after injection. Tylosin diffused from blood to the genital tract and accumulated in genital secretions whatever the stage of the oestrous cycle: the secretion to plasma ratio was 3.45 +/- 2.54 during oestrous and 4.75 +/- 3.24 during the luteal phase. The area under the concentration-time curve (AUC) and the mean residence time (MRT) were significantly higher in genital secretions than in plasma. The AUC and the MRT in genital secretions showed no significant differences during the oestrous cycle. The minimal inhibitory concentrations (MIC) of tylosin for 25 strains of Actinomyces pyogenes were between 0.032 (12 strains) and 0.063 micrograms ml-1 (13 strains). Simulations based on the mean values of pharmacokinetic parameters determined in genital secretions, gave tylosin concentrations higher than the MIC for at least 36 hours. It was concluded that after an intravenous administration of tylosin, effective concentrations were achieved in genital secretions of the cyclic cow whatever its hormonal status which supported its use for the treatment of genital tract infections.
authors.affiliation: Laboratoire associé de Physiopathologie et Toxicologie Expérimentales, Ecole Nationale Vétérinaire, Toulouse, France.
authors.forename: C C
authors.initials: CC
authors.lastname: Cester
authors.forename: J P
authors.initials: JP
authors.lastname: Ganiere
authors.forename: P L
authors.initials: PL
authors.lastname: Toutain
mesh_terms: D000190:Actinomyces / Q000187:drug effects; D000818:Animals; D002417:Cattle / Q000378:metabolism*; D004971:Estrus / Q000378:metabolism*; D005260:Female; D005836:Genitalia, Female / Q000378:metabolism*; D008954:Models, Biological; D015645:Tylosin / Q000097:blood / Q000493:pharmacokinetics* / Q000494:pharmacology
chemical_list: D015645:Tylosin