Comparative plasma pharmacokinetics of meloxicam in sheep and goats following intravenous administration

Meloxicam, a novel cyclooxygenase-2 selective nonsteroidal anti-inflammatory drug (NSAID), has been used extensively in humans and recently in some domestic animal species. Although it is an attractive NSAID for use in small ruminants, meloxicam pharmacokinetics have not been investigated in sheep and goats and this information is essential for rational therapeutic use of the drug in these species. In this investigation, comparative pharmacokinetic properties of meloxicam were studied in sheep and goats after a single intravenous dose of 0.5 mg kg(-1) body mass. Blood samples were collected via jugular venepuncture into heparinised tubes at predetermined times after drug administration. Plasma concentrations of meloxicam were determined by reversed-phase high performance liquid chromatography. The plasma concentrations of meloxicam were detectable in sheep and goats up to 72 and 48 h, respectively. The plasma concentration versus time data of meloxicam in both sheep and goats were adequately described by a two-compartment open model. The values obtained for sheep and goats for distribution half-life, volume of distribution at steady state and volume of the central compartment were almost similar in sheep and goats. The elimination half-life (t(1/2beta)), area under the plasma concentration-time curve (AUC), mean residence time (MRT) and total systemic clearance (Cl(B)) in sheep were significantly different from those of goats. The mean+/-S.E. values of t(1/2beta), MRT, AUC and Cl(B) in sheep were 10.85+/-1.21 h, 15.13+/-1.67 h, 31.88+/-2.97 microg h mL(-1) and 0.016+/-0.002 L h(-1) kg(-1), respectively whereas the respective values in goats were 6.73+/-0.58 h, 9.37+/-0.83 h, 19.23+/-2.23 microg h mL(-1) and 0.03+/-0.01 L h(-1) kg(-1). The results indicate that elimination kinetics of meloxicam differ significantly between sheep and goats and the elimination of the drug tends to be faster in goats compared to sheep.