title: Pharmacokinetics of azithromycin after intravenous and intramuscular administration to goats.
abstract: Azithromycin is the first of a class of antimicrobial agents designated azalides. The aim of the present study was to investigate the disposition pharmacokinetics of azithromycin in goats and determine its bioavailability. A cross-over study was carried out in two phases separated by 30 days. Azithromycin was administered at a single dose of 20 mg/kg body weight by i.v. and i.m. routes. Plasma concentrations of azithromycin were determined by a modified agar diffusion bioassay. After a single i.v. dose plasma concentrations were best fitted to a three-compartment open model. A two-compartment open model with first-order absorption fitted best after i.m. administration. The values of the pharmacokinetic parameters after i.v. administration were: half-life 32.5 h, apparent volume of distribution at the steady-state 34.5 L/kg, clearance 0.85 L/kg. and mean residence time (MRT) 40.1 h. After i.m. administration half-life of 45.2 h, a MRT of 60.3 h, maximum plasma concentration 0.64 mg/L and a bioavalability 92.2% were obtained. The pharmacokinetic parameters of azithromycin after i.m. administration, principally its long half-life and high bioavailability, could provide an alternative to the oral route of administration in goats, although more studies are needed to establish a suitable pharmaceutical formulation, propose optimun dosage regimens, investigate clinical efficacy and study the tolerability of repeated doses.
authors.affiliation: Department of Pharmacology, Faculty of Veterinary Medicine, University of Murcia, Murcia, Spain.
authors.forename: C M
authors.initials: CM
authors.lastname: Cárceles
authors.forename: A
authors.initials: A
authors.lastname: Font
authors.forename: A
authors.initials: A
authors.lastname: Espuny
authors.forename: E
authors.initials: E
authors.lastname: Fernández-Varón
authors.forename: J M
authors.initials: JM
authors.lastname: Serrano
authors.forename: E
authors.initials: E
authors.lastname: Escudero
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D019540:Area Under Curve; D017963:Azithromycin / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D018592:Cross-Over Studies; D006041:Goats / Q000378:metabolism*; D007273:Injections, Intramuscular / Q000662:veterinary; D007275:Injections, Intravenous / Q000662:veterinary; D008297:Male
chemical_list: D000900:Anti-Bacterial Agents; D017963:Azithromycin