Disposition of oxytetracycline in pigs after i.m. administration of two long-acting formulations

Two commercially available long-acting oxytetracycline (OTC) formulations were administered by the intramuscular (i.m.) route to six healthy pigs at the recommended dose of 30 mg/kg. After 2 h the mean maximum concentration (C(max)) reached values of 8.1 +/- 2.2 and 15.4 +/- 11.1 microg/mL, respectively. These concentrations remained higher than 0.5 microg/mL for more than 5 days after drug administration. The area under the concentration time curve (AUC09 days) of each formulation was 255 +/- 76.5 and 399.2 +/- 123 microg. h/mL, respectively, and the mean residence time (MRT) was around 3 days for both formulations. No significant differences were observed between the pharmacokinetic parameters of the two formulations, showing the bioequivalence of the two formulations studied according to the criteria established by the Food and Drug Administration (FDA) and the Committee for Veterinary Medicinal Products (CVMP).