title: Metabolism, Distribution, and Elimination of Mequindox in Pigs, Chickens, and Rats.
abstract: Mequindox (MEQ), a quinoxaline-N,N-dioxide antibacterial agent used to control bacterial enteritis in various food-producing animals, is a potential violative residue in food animal-derived products. The disposition and elimination of MEQ in rats, pigs, and chickens was comprehensively investigated to identify the marker residue and target tissue of MEQ in food animals for residue monitoring. Following a single oral administration, 62-71% of MEQ was rapidly excreted via urine and feces in all species within 24 h. Urinary excretion of radioactivity was 84 and 83.5% of the administered dose in rats and pigs, respectively. More than 92% of the administered dose was excreted in all species within 15 days. Radioactivity was found in nearly all tissues at the first 6 h after dosing, with the majority of radioactivity cleared within 4-6 days. The highest radioactivity and longest persisting time were found to be in the liver and kidney. Totals of 11, 12, and 7 metabolites were identified in rats, chickens, and pigs, respectively. No parent drug could be detected in any of the tissues of pigs and chickens. 3-Methyl-2-acetyl quinoxaline (M1), 3-methyl-2-(1-hydroxyethyl) quinoxaline-N4-monoxide (M4), and 3-methyl-2-(1-hydroxyethyl) quinoxaline-1,4-dioxide (M6) were the common and major metabolites of MEQ in all three species. Additionally, 3-methyl-2-(1-hydroxyethyl) quinoxaline (M5), 3-hydroxymethyl-2-ethanol quinoxaline-1,4-dioxide (M7), and 3-methyl-2-(1-hydroxyethyl) quinoxaline-N1-monoxide (M8) were the major metabolites of MEQ in rats, pigs, and chickens, respectively. M1 was designated to be the marker residue of MEQ in pigs and chickens. These results provide scientific data for the determination of marker residues and withdrawal time of MEQ in food animals and improve the understanding of the toxicity and disposition of MEQ in animals.
authors.affiliation: MOA Laboratory of Risk Assessment for Quality and Safety of Livestock and Poultry Products and ‡National Reference Laboratory of Veterinary Drug Residues (HZAU) and MAO Key Laboratory for Detection of Veterinary Drug Residues, Huazhong Agricultural University , Wuhan, Hubei 430070, China.
authors.forename: Lingli
authors.initials: L
authors.lastname: Huang
authors.affiliation: MOA Laboratory of Risk Assessment for Quality and Safety of Livestock and Poultry Products and ‡National Reference Laboratory of Veterinary Drug Residues (HZAU) and MAO Key Laboratory for Detection of Veterinary Drug Residues, Huazhong Agricultural University , Wuhan, Hubei 430070, China.
authors.forename: Fujun
authors.initials: F
authors.lastname: Yin
authors.affiliation: MOA Laboratory of Risk Assessment for Quality and Safety of Livestock and Poultry Products and ‡National Reference Laboratory of Veterinary Drug Residues (HZAU) and MAO Key Laboratory for Detection of Veterinary Drug Residues, Huazhong Agricultural University , Wuhan, Hubei 430070, China.
authors.forename: Yuanhu
authors.initials: Y
authors.lastname: Pan
authors.affiliation: MOA Laboratory of Risk Assessment for Quality and Safety of Livestock and Poultry Products and ‡National Reference Laboratory of Veterinary Drug Residues (HZAU) and MAO Key Laboratory for Detection of Veterinary Drug Residues, Huazhong Agricultural University , Wuhan, Hubei 430070, China.
authors.forename: Dongmei
authors.initials: D
authors.lastname: Chen
authors.affiliation: MOA Laboratory of Risk Assessment for Quality and Safety of Livestock and Poultry Products and ‡National Reference Laboratory of Veterinary Drug Residues (HZAU) and MAO Key Laboratory for Detection of Veterinary Drug Residues, Huazhong Agricultural University , Wuhan, Hubei 430070, China.
authors.forename: Juan
authors.initials: J
authors.lastname: Li
authors.affiliation: MOA Laboratory of Risk Assessment for Quality and Safety of Livestock and Poultry Products and ‡National Reference Laboratory of Veterinary Drug Residues (HZAU) and MAO Key Laboratory for Detection of Veterinary Drug Residues, Huazhong Agricultural University , Wuhan, Hubei 430070, China.
authors.forename: Dan
authors.initials: D
authors.lastname: Wan
authors.affiliation: MOA Laboratory of Risk Assessment for Quality and Safety of Livestock and Poultry Products and ‡National Reference Laboratory of Veterinary Drug Residues (HZAU) and MAO Key Laboratory for Detection of Veterinary Drug Residues, Huazhong Agricultural University , Wuhan, Hubei 430070, China.
authors.forename: Zhenli
authors.initials: Z
authors.lastname: Liu
authors.affiliation: MOA Laboratory of Risk Assessment for Quality and Safety of Livestock and Poultry Products and ‡National Reference Laboratory of Veterinary Drug Residues (HZAU) and MAO Key Laboratory for Detection of Veterinary Drug Residues, Huazhong Agricultural University , Wuhan, Hubei 430070, China.
authors.forename: Zonghui
authors.initials: Z
authors.lastname: Yuan
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000378:metabolism*; D002645:Chickens; D007668:Kidney / Q000737:chemistry / Q000378:metabolism; D008099:Liver / Q000737:chemistry / Q000378:metabolism; D015394:Molecular Structure; D011810:Quinoxalines / Q000737:chemistry / Q000378:metabolism*; D051381:Rats; D013552:Swine; D014018:Tissue Distribution
chemical_list: D000900:Anti-Bacterial Agents; C545385:Mequindox; D011810:Quinoxalines
keywords: [3H]-mequindox; excretion; isotopic tracing; marker residue; metabolism; target tissue; tissue depletion