Non-bioequivalence of various trademarks of enrofloxacin and Baytril (R) in cows

Including Baytril((R)), in various parts of the world many commercial prepa rations of enrofloxacin for parenteral administration are being employed fo r the treatment of bacterial diseases in cows. To optimize clinical respons es and to minimize development of bacterial resistance to this agent, the c opied pharmaceutical preparations must comply with some key pharmacokinetic features when bioequivalence studies are performed. To assess whether or n ot there was bioequivalence among nine commercial preparations of enrofloxa cin and the original one, a controlled pharmacokinetic study was carried ou t. These was done utilizing the microbiological agar-diffusion test as quan titative/qualitative analytical method. A non-compartmental model defined k inetic variables. Results for Baytril revealed that maximal serum concentra tion (Cs-max) was only matched by one preparation while area under the curv e (AUC) of the serum concentration/activity of enrofloxacin and metabolites in time was not matched by any preparation. Time to Cs-max (T-max), elimin ation half-life, and shape of the time-serum concentrations of enrofloxacin profiles obtained for the nine generic preparations differ significantly s omehow from the corresponding data obtained for the reference enrofloxacin. The need for studies to demonstrate bioequivalence becomes mandatory if si milar preparations of enrofloxacin become commercially available. Enrofloxa cin should be used selectively and cautiously to limit development of bacte rial resistance. Non-bioequivalence of relevant pharmacokinetic values, suc h as Cs-max. and bioavailavility (AUC) would facilitate development of bact erial resistance and limit the useful life span of this antibacterial agent .