Pharmacokinetics of Enrofloxacin in Emu (Dromaius novaehollandiae) Birds After Intravenous and Oral Bolus Administration

Abstract

Pharmacokinetics of enrofloxacin was studied after intravenous and oral bolus administration at 10 mg/kg in healthy emus aged between 18 and 24 months. Blood samples were collected from jugular vein at predetermined time intervals after drug administration. Enrofloxacin and its active metabolite ciprofloxacin in plasma were determined by HPLC. Plasma concentrations versus time were analyzed by a non-compartmental analysis. For i.v. and oral bolus dose of administration, elimination half-life (t1/2β) was 4.364 ± 0.179 and 4.125 ± 0.361 h, respectively; AUC0–∞ was 20.085 ± 3.493 and 16.056 ± 1.436 µg h/mL, respectively; mean residence time (MRT) was 5.105 ± 0.216 and 6.616 ± 0.475 h, respectively; volume of distribution was 3.921 ± 1.005 and 3.171 ± 0.296 L/kg, respectively and total body clearance was 0.629 ± 0.164 and 0.507 ± 0.003 L/h kg, respectively. Mean absolute bioavailability for enrofloxacin after oral administration was 79.941 ± 7.147 %. The metabolite ciprofloxacin could be detected from 15 min to 24 h following i.v. and oral administration of enrofloxacin. The ratio of AUC0–tcipro/AUC0–tenro was 7.764 and 9.031 %, respectively for i.v. and oral administration of enrofloxacin. The t1/2β and MRT of the metabolite were longer than those of parent substance. From the PK/PD indices such as Cmax/MIC, AUC/MIC and Cmax/MPC, AUC/MPC study, the recommended doses of enrofloxacin in emu birds were 10 mg/kg body weight once daily for i.v. and oral routes against organisms susceptible to 0.25 and 0.125 μg/mL, respectively. Taking the PAE and active metabolite ciprofloxacin into consideration, it is recommended that enrofloxacin could be used at the dose rate of 10 mg/kg at every 24 h even against the organisms susceptible to 0.5 µg/mL.