A bioequivalence and pharmacokinetic evaluation of two commercial diminazene aceturate formulations administered intramuscularly to cattle.

The bioequivalence of the diminazene formulation Veriben (Centaur) was determined in cattle (n = 10) by means of a single-dose, randomized cross-over experiment. The results of nine statistical procedures commonly used for bioequivalence evaluation are discussed. Veriben was found to be equivalent to Berenil (Hoechst) with respect to the area under the plasma concentration versus time curve, but not in terms of the maximum plasma drug concentration and the time to maximum plasma drug concentration. Pharmacokinetic parameters were calculated in which bioequivalence data (n = 10) together with data from an additional four cattle were used. A two-compartment model best described the pharmacokinetic behaviour of diminazene in cattle. Peak concentrations of diminazene (3.24 +/- 0.16 micrograms/ml) were reached 49.8 (+/- 7.6) min after intramuscular injection of 3.5 mg/kg drug, with absorption proceeding rapidly (t1/2 alpha = 1.93 +/- 0.95 h). Diminazene was slowly eliminated (t1/2 beta = 222 h), resulting in a mean residence time of 13.27 d. The safe interval necessary between successive treatments of diminazene or before live babesia vaccines should be administered, and a recommended pre-slaughter withdrawal period are also discussed.