Plasma concentrations of flunixin in the horse: its relationship to thromboxane B2 production.
The effects of the intravenous (i.v.) administration of 1.1 mg/kg of flunixin meglumine on thromboxane B2 (TxB2) concentrations were studied in sedentary and 2-year-old horses in training. The baseline TxB2 serum concentrations generated during clotting were 2.89 +/- 0.81, 2.19 +/- 0.25 and 0.88 +/- 0.12 ng/ml for the 2-year-old Thoroughbreds in training, sedentary horses under 10 and over 10 years old, respectively. There was a significant difference in baseline TxB2 concentrations between older and younger horses (P less than 0.005). Significant reduction in TxB2 production from baseline were noted at 1 (P less than 0.01) and 4 h (P less than 0.01) but not at 8 h after flunixin administration. The percent reduction in serum TxB2 concentration at 1 h after the administration of flunixin was 68.6 +/- 7.3 and 45.2 +/- 6.8 for the training and sedentary horses, respectively; the differences were significant (P less than 0.04). Serum concentrations of TxB2 returned to baseline values by 12-16 h after flunixin administration. The results of this study indicate a difference in the TxB2 concentrations of older vs. younger horses and a difference in the suppression of TxB2 after the administration of flunixin in 2-year-old Thoroughbreds in training compared to sedentary horses. The results of this study suggest that the detection of low concentrations of flunixin in urine 24 h post-administration may not represent pharmacologic effective concentrations of flunixin in plasma.
Soma
L R
LR
Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Kennett Square 19348.
Uboh
C E
CE
Rudy
J
J
Fegely
J
J
D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000008:administration & dosage / Q000097:blood*; D003002:Clonixin / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000097:blood; D006736:Horses / Q000097:blood*; D007275:Injections, Intravenous / Q000662:veterinary; D007958:Leukocyte Count / Q000662:veterinary; D010805:Physical Conditioning, Animal; D010976:Platelet Count / Q000662:veterinary; D013929:Thromboxane B2 / Q000096:biosynthesis* / Q000097:blood
D000894:Anti-Inflammatory Agents, Non-Steroidal; D013929:Thromboxane B2; C014558:flunixin meglumine; D003002:Clonixin