Disposition Kinetics of Levofloxacin in Sheep after Intravenous and Intramuscular Administration

The present study was planned to investigate the disposition kinetics of levofloxacin in plasma of female native Barky breed sheep after single intravenous (IV) and intramuscular (IM) administration of 4 mg/kg body weight. The concentrations of levofloxacin in the plasma were measured using high-performance liquid chromatography (HPLC) with a UV detector on samples collected at 0, 0.08, 0.16, 0.33, 0.5, 1, 2, 4, 6, 8, 10, 12, 18, 24, 32, and 48 h after treatment. Following intravenous injection, the decline in plasma drug concentration was biexponential with half-lives of (t(1/2α)) 0.33 ± 0.12 h and (t(1/2β)) 3.29 ± 0.23 h for distribution and elimination phases, respectively. The volume of distribution at steady state V((d(ss))) was 0.86 ± 0.23 l/kg. After intramuscular administration of levofloxacin at the same dose, the peak plasma concentration (C(max)) was 3.1 ± 0.35 μg/mL and was obtained at 1.64 ± 0.29 h (T(max)), the elimination half-life (T(1/2el)) was 3.58 ± 0.30 h, and AUC was 20.24 ± 1.31 μg.h/mL. The systemic bioavailability was 91.35 ± 6.81 %. In vitro plasma protein binding was 23.74%. When approved therapy fails, levofloxacin may be used in some countries for therapy of food animals, however, that is not true in the US.