Pharmacokinetics, metabolism and urinary detection time of flunixin after intravenous administration in camels

The pharmacokinetics of flunixin were determined after an intravenous dose of 1.1 mg/kg body weight in six camels and 2.2 mg/kg body weight in four camels. The data obtained (mean +/- SEM) for the low and high dose, respectively, were as follows: The elimination half-lives (t(1/2 beta)) were 3.76 +/- 0.24 and 4.08 +/- 0.49 h, the steady state volumes of distribution (Vd(ss)) were 320.61 +/- 38.53 and 348.84 +/- 35.36 mL/kg body weight, total body clearances (Cl-T) were 88.96 +/- 6.63 and 84.86 +/- 4.95 mL/h/kg body weight and renal clearances (Cl-r) were 0.52 +/- 0.09 and 0.62 +/- 0.18 mL/h/kg body weight. A hydroxylated metabolite of flunixin was identified by gas chromatography/mass spectrometry (GC/MS) under electron and chemical ionization and its major fragmentation pattern was verified by tandem mass spectrometry (GC/MS/MS) using neutral loss, daughter and parent scan modes. The detection times for flunixin and its hydroxylated metabolite in urine after an intravenous (i.v.) dose of 2.2 mg/kg body weight were 96 and 48 h, respectively.