Disposition kinetics and bioavailability of danofloxacin in Mehsana buffalo calves after parenteral administration

The present study was undertaken to investigate the pharmacokinetics of danofloxacin following single-dose intravenous (IV) and intramuscular (IM) administration at 5.0 mg/kg body weight in Mehsana buffalo calves (n = 6). Plasma concentrations of danofloxacin were determined using a validated high-performance liquid chromatography (HPLC) method, and pharmacokinetic parameters were derived by non-compartmental analysis. Following IV administration, danofloxacin exhibited rapid systemic distribution with a high initial plasma concentration (9.55±0.49 µg/ml at 0.033 h) and a biphasic decline thereafter. The mean elimination rate constant (β) was 0.13±0.00 h⁻¹, corresponding to an elimination half-life (t½β) of 5.24±0.15 h. The mean AUC₀-∞ was 12.69±0.23 µg·h/ml, mean residence time (MRT) was 5.77±0.07 h, steady-state volume of distribution (Vdss) was 2.28±0.02 L/kg, and total body clearance (ClB) was 0.39±0.01 L/h/kg, indicating extensive tissue distribution and moderate elimination. Following IM administration, danofloxacin was rapidly absorbed, achieving a mean maximum plasma concentration (Cmax) of 2.09±0.14 µg/ml at a mean Tmax of 0.83±0.11 h. The elimination half-life (6.92±0.57 h) and mean residence time (10.08±0.89 h) were longer than those observed after IV administration, indicating prolonged systemic persistence. The mean AUC₀-∞ following IM administration was 17.04±1.53 µg·h/ml, resulting in a high apparent systemic bioavailability (127%), suggestive of near-complete absorption from the injection site. The pharmacokinetic profile observed in Mehsana buffalo calves demonstrates rapid absorption, extensive tissue distribution, and sustained systemic exposure of danofloxacin, supporting its suitability for intramuscular administration