Pharmacokinetics and bioavailability of doxycycline in Thai native chickens

The pharmacokinetic characteristics of long acting (LA) doxycycline (DOX) formulation were observed in healthy Thai native chickens. Each animal was administered either intravenously (i.v.) or intramuscularly (i.m.) with a single dosage of DOX LA (20 mg/kg body weight). Plasma DOX levels were determined using the agar-well bioassay technique. DOX disposition fitted an open two-compartment model. The maximal plasma concentration (C max ) was 4.59 + 0.59 µg/ml at 20 min with bioavailability of 88.11 + 3.07% after i.m. administration. The elimination half-life (t 1/2β ), apparent volume of distribution (V d ), elimination rate constant (k el ) and total body clearance (Cl B ) were 14.13 + 1.11 h, 0.901 + 0.027 l/kg, 0.34 + 0.04 h -1 and 0.31 + 0.04 l.h -1 /kg, respectively, following i.v. administration. Based on the pharmacokinetic results, therapeutic level of DOX Therefore, the dosage regimen of 20 mg/kg bw administered intramuscularly is recommended every 60 h in Thai native chickens.