Reduced resident time and tissue residues of synergistic florfenicol-thiamphenicol combination in Leghorn chickens.

Abstract

Received: Revised: Accepted: Published online: September 24, 2018 October 25, 2018 October 28, 2018 January 24, 2019 In vivo synergistic antimicrobial effects against pathogens in chickens have been reported for florfenicol (FF) and thiamphenicol (TAP) at a ratio of 1:2. The present study evaluates the pharmacokinetics and tissue residues of a single combined intramuscular treatment of FF+TAP at 1/6 and 1/3 of their respective recommended doses in 5-week old broiler chickens. The drug concentrations were determined by LC/MS/MS. Significant reductions were observed in the Cmax (0.045 and 2.64 μg/mL for FF and TAP, respectively) and AUC (0.13 and 7.19 h∙μg/mL for FF and TAP, respectively) compared to corresponding values reported for the recommended dose (up to two orders of magnitude lower). Tissue FF (10.6-88.4 μg/kg) and TAP concentrations (6.5-147.0 μg/kg) declined below the maximum residue limit within only one day except for TAP residue in skin/fat. This experiment provided supporting evidence for a complete study that synergistic FFTAP has potential benefits over monotherapy since drug residues could be greatly reduced; much shorter withdrawal period was strongly indicated. ©2018 PVJ. All rights reserved