Pharmacokinetics and pharmacodynamics of tolfenamic acid in calves.
Pharmacokinetic/pharmacodynamic modelling was applied to a study in which tolfenamic acid was administered intravenously to calves at a dose rate of 2 mg kg-1. The drug had a shorter mean (SEM) elimination half-life (T1/2 beta) of 2.5 (0.95) hours and a larger volume of distribution (Vdarea) of 0.98 (0.28) litre kg-1 than other non-steroidal anti-inflammatory drugs. Its body clearance was high with a mean value of 0.30 (0.06) litre kg-1 h-1. It had inhibitory effects on inflammatory exudate PGE2 and beta-glucuronidase, serum TxB2 and bradykinin-induced swelling but it did not affect exudate LTB4 concentrations. Its mean EC50 values were lower for exudate PGE2, beta-glucuronidase and bradykinin-induced swelling inhibition (0.077 [0.018]; 0.040 [0.017] and 0.030 [0.020] microgram ml-1, respectively) than for serum TxB2 inhibition (0.137 (0.079) microgram ml-1). There were also differences in its equilibration halflife, which was short for the inhibition of serum TxB2, intermediate for exudate PGE2 and beta-glucuronidase and longer for bradykinin-induced swelling. These differences may be explained by the existence of three distribution compartments relating to the different sites of action of the drug.
Landoni
M F
MF
Department of Veterinary Basic Sciences, Royal Veterinary College, Hatfield, Hertfordshire.
Cunningham
F M
FM
Lees
P
P
D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000097:blood / Q000493:pharmacokinetics* / Q000494:pharmacology*; D001920:Bradykinin / Q000494:pharmacology; D002417:Cattle; D015232:Dinoprostone / Q000378:metabolism; D005966:Glucuronidase / Q000378:metabolism; D006207:Half-Life; D007249:Inflammation / Q000503:physiopathology; D007275:Injections, Intravenous; D008657:Metabolic Clearance Rate; D008954:Models, Biological; D013929:Thromboxane B2 / Q000378:metabolism; D062367:ortho-Aminobenzoates / Q000097:blood / Q000493:pharmacokinetics* / Q000494:pharmacology*
D000894:Anti-Inflammatory Agents, Non-Steroidal; D062367:ortho-Aminobenzoates; C009500:tolfenamic acid; D013929:Thromboxane B2; D005966:Glucuronidase; D015232:Dinoprostone; D001920:Bradykinin