Disposition of oxytetracycline in the bovine genital tract: systemic vs intrauterine administration.

The distribution of oxytetracycline (OTC) in genital tissues, uterine secretions, milk, and plasma was examined after systemic (IM) and intrauterine (IU) administration at various intervals after administration in normal-cycling diestrous cows and in cows with chronic endometritis. The IM route resulted in OTC concentrations in endometrium and uterine secretions that were higher than were concentrations in plasma and milk over 72 hours. Twenty-four hours after IM administration, OTC concentrations in tissues of the genital tract (ovaries, oviducts, myometrium, serosa, cervix, and vagina), muscles, and udder were 100% higher than were concentrations in plasma. The IU administration resulted in a high concentration in the endometrium and uterine cavity over the 72-hour posttreatment period. The plasma concentrations were considerably lower than after the IM injection, indicating a lesser absorption from the uterus than from the IM injection site. This was more pronounced in cows with endometritis. Elimination from plasma and milk occurred in 24 hours. Contrary to results of the IM route, the IU route did not result in detectable concentrations in genital tissues apart from the endometrium 24 hours after administration.