Strategic administration of enrofloxacin in poultry to achieve higher maximal serum concentrations

To achieve a higher maximal serum concentration (Cs-mas) of enrofloxacin after oral administration of 10 mg/kg/day of three commercial preparations of enrofloxacin to chickens, two concentrations of the drug were tested (0.1 and 0.2%), under controlled laboratory conditions. A single oral bolus dose was delivered directly into the proventriculus of each of 240 chickens, which were equally divided into six groups: three received the customary concentration (0.1%), and three received the higher concentration. A quantitative/qualitative microbiological analytical method to determine serum concentrations of enrofloxacin and a software program to obtain pharmacokinetic variables, revealed that time vs. concentration relationships best fitted double peak shape curves, Cs-max1, and Cs-max2. Statistically significant (P > 0.01) increments were obtained when 0.2% enrofloxacin oral solutions from the three different commercial preparations were administered. The increments ranged from 175% to 338% for Cs-max1 and 69% to 342% for Cs-max2. Optimal bactericidal concentrations of enrofloxacin are usually twice the value of their minimal inhibitory concentration. Although clinical trials are now required, it would appear that increments in the serum concentration of enrofloxacin may reduce to the rate at which bacterial resistance occurs and so increase clinical efficacy without affecting the cost per treatment. (C) 2003 Elsevier Science Ltd. All rights reserved.