title: Pharmacokinetics of doxycycline in broiler chickens.
abstract: Doxycycline was given to two groups of eight chickens at a dose of 20 mg/kg of body weight, intravenously (i.v.) or orally. Plasma concentration was monitored serially for 12 h after each administration. Another group of 30 chickens was given 20 mg/kg orally every 24 h for 4 days, and plasma and tissue concentrations determined serially after the last administration. Concentrations of doxycycline were measured using high-performance liquid chromatography. Pharmacokinetic variables were calculated, using a two-compartment open model. The elimination half-life and the mean residence time for plasma were 6.03 +/- 0.45 and 7.48 +/- 0.38 h, respectively, after oral administration and 4.75 +/-0.21 and 2.87 +/-0.11 h, respectively, after i.v. administration. After single oral administration, doxycycline was absorbed rapidly, with T(max) of 0.35 +/- 0.02 h. Maximum plasma concentration was 54.58 +/- 2.44 mu/ml. Oral bioavailability of doxycycline was found to be 41.33 +/- 2.02%. Doxycycline was widely distributed in tissues and considerable concentrations were found following oral administration of 20 mg/kg on four successive days. The results indicate that doxycycline concentrations were cleared slowly and were at or below the accepted drug tolerance levels in the marker tissues within 5 days after dosing.
authors.affiliation: Departamento de Toxicologia, Instituto de Farmacologia y Toxicologia, CSIC, Facultad de Veterinaria, Universidad Complutense de Madrid, Madrid, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Anadon
authors.forename: M R
authors.initials: MR
authors.lastname: Martinez-Larranaga
authors.forename: M J
authors.initials: MJ
authors.lastname: Diaz
authors.forename: P
authors.initials: P
authors.lastname: Bringas
authors.forename: M C
authors.initials: MC
authors.lastname: Fernandez
authors.forename: M L
authors.initials: ML
authors.lastname: Fernandez-Cruz
authors.forename: J
authors.initials: J
authors.lastname: Iturbe
authors.forename: M A
authors.initials: MA
authors.lastname: Martinez