Bioequivalence of a Preparation of Tulathromycin in Cattle

Testing the quality of antibacterial pharmaceutical preparations that can be regarded as generic is of utmost importance to ensure sustainable medical practices. Hence, comparative pharmacokinetics studies become necessary. In this trial, a new pharmaceutical preparation of tulathromycin (TTM) was submitted to a bioequivalence test, taking the reference preparation of this macrolide derivative as control i.e., the commercial preparation of TTM containing 100 mg of the drug Pisadrax ® , manufactured by PiSA Agropacuaria S.A. de C.V. and the reference brand of TTM Draxxin ® (Zoetis, Mexico). Twenty-four young steers Charolais/Brahman randomly divided into two groups of twelve animals each, received a single injection of 2.5 mg/kg subcutaneously of either preparation. A validated HPLC-masses analytical technique of plasma concentrations of tulathromycin was used to determine TTM plasma concentrations at fixed intervals for 240 h. The key pharmacokinetic parameters were obtained by compartmental and non-compartmental analysis. Results show that the experimental preparation of tulathromycin (Pisadrax ® ) can be regarded as bioequivalent to the reference one (Draxxin ® ) in steers, given that AUC0-240, MRT, and K½el values from both preparations resulted statistically indistinguishable and with confidence interval > 95%.