Enrofloxacin comparative pharmacokinetics of oral gavage and pulsed administration in turkey

Enrofloxacin (ENRO) is a 2nd generation quinolones used in valuable food and companion animals to control infection caused by various Gram-negative bacteria. ENRO use should be restricted to a highly individualized therapy, but it is also authorized for mass medication in food-producing species including avian species and turkeys. ENRO was orally administered to healthy turkey via gavage as a single bolus and via 10 h pulsed medicated water for 5 consecutive days at the dose of 10 mg/kg. Blood samples were taken between 0.25 and 24 h for the bolus administration, and between 1 and 22 h at the 5th day of administration for the pulsed medicated water. ENRO serum concentrations were determined by a validated LC/MS/MS method. Plasma concentrations vs time were analyzed by mono and non-compartmental analysis (WinNonLin 6.1). The ENRO active metabolite, ciprofloxacin (CIPRO) was quantified at very small amounts and the results are reported as the sum of ENRO plus CIPRO concentrations. After bolus ENRO reached mean peak serum concentration (Cmax 1.53±0.31µg/mL) at about 2 hours (Tmax 1.88±0.33 h) and mean AUC(0-24) and t1/2el were 12.74±1.52 hr.µg/mL and 6.58±1.82 h, respectively. Following pulsed administration on day 5 Cmax of 0.67±0.18, Tmax 6.86±2.48, AUC(0-24) 7.37±1.07 and t1/2el 5.31±0.63 were observed. ENRO plus CIPRO serum concentrations after 10 h/day medicated water for 5 days were significantly lower than those obtained after the single bolus. The results indicate that adequate drug serum concentrations cannot be attained following ENRO treatment via pulsed medicated water at the EU authorized dosage of 10 mg/kg; this could reduce the effectiveness of the antimicrobial treatment and contribute to the diffusion of resistance.