DefinePK

Abstract

A parallel designed study was conducted in 24 healthy calves of both sexes post weaning to investigate the bioequivalence of two long acting oxytetracycline OTC formulations. Plasma disposition kinetics were studied for spectropan LA compared to terramycin L.A, as reference standard, following intramuscular administration IM at a dose of 20 mg/kg b.wt. Validated high performance liquid chromatography method HPLC was used for determination of oxytetracycline in plasma with 99% recovery and 1.2% coefficient of variation. Scatterplot and Bland-Altman plot indicated the identical relationship between both products plasma OTC concentrations with average difference of 0.06 µg/mL. Cmax values of 3.28±0.125 and 3.21±0.231 µg/mL were achieved at 3.67±0.534 and 3.66±0.450 h post-administration for both spectropan and terramycin, respectively. Plasma concentration sustained above 0.5 µg/mL for more than 72 h post injection. The hastened OTC elimination probably attributed to, the effect of increased water consumption post weaning, in addition to breed variation. Almost all estimated kinetic parameters; Cmax, Tmax, AUC0-96, AUC0-?, AUMC0-? and Kel, show no statistically significant difference between both formulations. Westlake’s 90% confidence intervals of either untransformed or transformed log of AUC0-96, AUC0-?, Cmax and Tmax, did fall within the 80-125% range for both tested formulations. According to, the guidelines implemented by the Committee for Veterinary Medicinal Products (CVMP) and the Food and Drug Administration (FDA), both studied formulations are bioequivalent.