Oral pharmacokinetics and bioavailability of roxithromycin in broiler chickens using HPLC

Abstract

The present study was designed to investigate the oral pharmacokinetics and bioavailability of roxithromycin, a macrolide class antimicrobial drug, in broiler chickens at a single dose of 20 mg/kg body weight. Plasma concentrations of roxithromycin were measured by High Performance Liquid Chromatography (HPLC) method using UV (ultraviolet) detector. The pharmacokinetic (PK) parameters were calculated from plasma concentrations versus time data using ‘PK Solver 2.0’ software. Following single intravenous administration, the volume of distribution at steady state (V_ss) and total body clearance (Cl) were 3.04 L/kg and 0.45 L/hr/kg, respectively. Following oral administration of roxithromycin at the dose rate of 20 mg/kg body weight in broilers, a characteristic short lag phase of 15 minutes in absorption was observed and thereafter mean maximal plasma concentration (C_max: 3.60 μg/ml) was achieved at 2 hr. The mean values of elimination half-life (t_1/2β) and mean resident time (MRT) were 8.30 and 9.57 hr, respectively. Calculated oral bioavailability (F) ranged from 51.95 to 62.57% with a mean value of 56.86%. Based on pharmacokinetic-pharmacodynamic (PK-PD) integration efficacy predictor, oral dose at 20 mg/kg body weight of roxithromycin twice a day, is predicted to be effective for treating the susceptible bacterial infections in the broiler chickens with a MIC value ≤ 1.0 μg/ml.