title: Lactose conjugation of sulphonamide drugs in the lactating dairy cow.
abstract: 1. 14C-Sulphamethazine (4-amino-N-(4,6-dimethyl-2-pyrimidinyl)benzene-[U-14C]-sulphonamide; 220 mg/kg of body weight) was given orally or i.v. to lactating dairy cows. Milk collected from 0-48 h after dosing accounted for 2.0% (oral dose) and 1.1% (i.v. dose) of the total 14C-activity administered. 2. Sulphamethazine accounted for 70-79% (oral dose) and 54-75% (i.v. dose) of the total 14C in milk samples collected from 0-48 h after dosing. N4-acetylsulphamethazine accounted for 1-2% (oral dose) and 1-4% (i.v. dose) of the 14C in milk. 3. The major 14C-labelled metabolite in the milk was isolated and identified as the N4-lactose conjugate of sulphamethazine, a unique type of metabolite not previously reported. This metabolite accounted for 10-14% (oral dose) and 9-20% (i.v. dose) of the 14C-activity in the milk collected from 0-48 h after dosing with 14C-sulphamethazine. 4. N4-lactose conjugates of sulphapyridine, sulphamerazine, sulphathiazole, sulphadimethoxine and sulphaquinoxaline were present in the milk from cows orally dosed with these five sulphonamide drugs.
authors.affiliation: Biosciences Research Laboratory, US Department of Agriculture, Fargo, ND 58105.
authors.forename: G D
authors.initials: GD
authors.lastname: Paulson
authors.forename: V J
authors.initials: VJ
authors.lastname: Feil
authors.forename: J M
authors.initials: JM
authors.lastname: Giddings
authors.forename: C H
authors.initials: CH
authors.lastname: Lamoureux
mesh_terms: D000818:Animals; D002250:Carbon Radioisotopes; D002417:Cattle / Q000378:metabolism*; D005260:Female; D007774:Lactation; D007785:Lactose / Q000378:metabolism*; D008892:Milk / Q000737:chemistry*; D013449:Sulfonamides / Q000378:metabolism*
chemical_list: D002250:Carbon Radioisotopes; D013449:Sulfonamides; D007785:Lactose