title: Pharmacokinetics of azithromycin after i.v. and i.m. administration to sheep.
abstract: The pharmacokinetics (PK) of azithromycin after i.v. and i.m. injection at a single dosage of 20 mg/kg bodyweight was studied in sheep. Blood samples were collected from the jugular vein until 120 h after dosing for both routes. Plasma concentrations of azithromycin were determined by bioassay. The plasma concentration-time data of azithromycin best fitted a three-compartment model after i.v. administration and a two-compartment model with first-order absorption after i.m. administration. The elimination half-life (t(1/2lambdaz)) was 47.70 +/- 7.49 h after i.v. administration and 61.29 +/- 13.86 h after i.m. administration. Clearance value after i.v. dosing was 0.52 +/- 0.08 L/kg.h. After i.m. administration a peak azithromycin concentration (C(max)) of 1.26 +/- 0.19 mg/L was achieved at 1.24 +/- 0.31 h (t(max)). Area under the curve (AUC) were 38.85 +/- 5.83 mg.h/L and 36.03 +/- 1.52 mg.h/L after i.v. and i.m. administration respectively. Bioavailability obtained after i.m. administration was 94.08 +/- 11.56%. The high tolerability of this i.m. preparation and the favourable PK behaviour such as the long half-life and high bioavailability make azithromycin likely to be effective in sheep.
authors.affiliation: Department of Pharmacology, Faculty of Veterinary Medicine, University of Murcia, Campus de Espinardo, Murcia, Spain.
authors.forename: C M
authors.initials: CM
authors.lastname: Cárceles
authors.forename: A
authors.initials: A
authors.lastname: Font
authors.forename: E
authors.initials: E
authors.lastname: Escudero
authors.forename: A
authors.initials: A
authors.lastname: Espuny
authors.forename: P
authors.initials: P
authors.lastname: Marín
authors.forename: E
authors.initials: E
authors.lastname: Fernández-Varón
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*; D001825:Body Fluid Compartments; D002626:Chemistry, Pharmaceutical; D005260:Female; D007273:Injections, Intramuscular / Q000662:veterinary; D007275:Injections, Intravenous / Q000662:veterinary; D012756:Sheep / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D017963:Azithromycin