Pharmacokinetics and Tissue Levels of Tilmicosin in Fowls

Abstract

Tilmicosin is a long-acting macrolide antibiotic used in the treatment of respiratory disease. It was administered once (SO mg/kg b.wt) to fowls via the oral route for determination of kinetic properties and tissue levels. After oral administration, tilmicosin's pharmacokinetics conformed to a two compartment open model. Tilmicosin was slowly eliminated from the serum and lung with mean half-lives of 30.18 +/- 2.38 and 75.74 +/- 3.67 hours, respectively The mean maximum concentration of the drug in the lungs was found to be 6.2 times greater that of serum. Serum and lung tilmicosin concentrations reached peak Values 4.66 +/- 2 and 17.78 +/- 7.51 hours, respectively, after oral administration. In fowls, the apparent volume of distribution was found to be more than 1 L/kg, indicating extensive tissue distribution. The clearance Values were calculated to be 1.33 +/- 0.06 for serum and 0.11 +/- 0.004 Vh for lung. After oral administration, tilmicosin appeared to be retained at higher concentrations and for longer times in the edible tissue than in serum. The mean peak concentrations of tilmicosin were obtained in kidney 8 hours after dosing and in liver, heart and muscles 12 hours after dosing. Then, tissue concentrations decreased slowly over time and tilmicosin residues were only detected in the liver and kidney.