Comparative Pharmacokinetics of Two Injection Formulations of Tulathromycin after a Single Intramuscular Administration in Healthy Swine

The objective of this study was to campare different pharmacokinetic parameters of a locally manufactured (Tulathromycin Injection, CONTINENT, China) and reference (Draxxin, Pfizer, USA) formulation of tulathromycin 2.5 mg injection after intramuscular administration of a single dose. Twelve pigs were randomly allocated to two treatment groups. Blood samples were collected by venipuncture of the jugular vein. or anterior vena cava, plasma samples were analyzed by High-Performance Liquid Chromatography (HPLC) with tandem mass spectrometry detection (LC-MS/MS) using ESI. Mean puls or minus Standard Deviation (SD) of peak plasma Concentration (C-max) Area Under the serum Concentration-time curve (AUC(0-t)), Area Under the serum Concentration-time curve (AUC(inf)), serum concentration half-life (t(1/2)) were 4.32 +/- 1.52 and 5.86 +/- 1.28 mu g mL(-1), 3.98 +/- 1.63 and 4.24 +/- 1.30 mu gh mL(-1), 4.04 +/- 1.67 and 4.65 +/- 2.01 mu gh mL(-1), 83.55 +/- 12.84 and 79.25 +/- 10.64 h for the locally manufactured (tested) and reference formulation, respectively. The 90% confidence intervals of the mean of the difference between log-transformed values for AUC(0-360), AUC(0-infinity) and C-max within the bioequivalence accepted range of 80-125%. The results indicate that tulathromycin was rapidly absorbed, eliminated slowly and highly bioavailable following a single dose which make tulathromycin likely to be effective in swine.