title: Pharmacokinetic profile and in vitro selective cyclooxygenase-2 inhibition by nimesulide in the dog.
abstract: The pharmacokinetic properties and in vitro potency of nimesulide, a nonsteroidal anti-inflammatory drug (NSAID) were investigated in 8 or 10 dogs after intravenous (i.v.), intramuscular (i.m.) and oral (single and multiple dose) administrations at the nominal dose of 5 mg/kg. After i.v. administration, the plasma clearance was 15.3 +/- 4.2 mL/kg/h, the steady-state volume of distribution was low (0.18 +/- 0.011 L/kg) and the elimination half-life was 8.5 +/- 2.1 h. After i.m. administration, the terminal half-life was 14.0 +/- 5.3 h indicating a slow process of absorption with a maximum plasma concentration (6.1 +/- 1.5 microg/mL) at 10.9 +/- 2.1 h postadministration and the systemic bioavailability was 69 +/- 22%. After oral administration in fasted dogs, the maximal plasma concentration (10.1 +/- 2.7 microg/mL) was observed 6.1 +/- 1.6 h after drug administration, the plasma half-life was 6.2 +/- 1.9 h and the mean bioavailability was 47 +/- 12%. After daily oral administrations for 5 days, the average plasma concentration during the fifth dosage interval was 8.1 +/- 2.9 microg/mL and the overall bioavailability was 58 +/- 16%. The mean accumulation ratio was 1.27 +/- 0.4. In vitro nimesulide inhibitory potencies for cyclooxygenase (COX)-1 and COX-2 isoenzymes were determined using a whole blood assay. Canine clotting blood was used to test for inhibition of COX-1 activity and whole blood stimulated by lipopolysaccharide (LPS) was used to test for inhibition of COX-2 activity. The inhibitory concentration (IC50) for inhibition of COX-2 and COX-1 were 1.6 +/- 0.4 microM (0.49 +/- 0.12 microg/mL) and 20.3 +/- 2.8 microM (6.3 +/- 0.86 microg/mL) giving a nimesulide COX-1/COX-2 ratio of 12.99 +/- 3.41. It was concluded that at the currently recommended dosage regimen (5 mg/kg), the plasma concentration totally inhibits COX-2 and partly inhibits COX-1 isoenzyme.
authors.affiliation: Unité Associée INRA de Physiopathologie et Toxicologie Expérimentales, Ecole Nationale Vétérinaire de Toulouse, Toulouse, France. pl.toutain@envt.fr
authors.forename: P L
authors.initials: PL
authors.lastname: Toutain
authors.forename: C C
authors.initials: CC
authors.lastname: Cester
authors.forename: T
authors.initials: T
authors.lastname: Haak
authors.forename: S
authors.initials: S
authors.lastname: Metge
mesh_terms: D000284:Administration, Oral; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000494:pharmacology*; D001682:Biological Availability; D051546:Cyclooxygenase 2; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors / Q000493:pharmacokinetics / Q000494:pharmacology; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D007273:Injections, Intramuscular; D007275:Injections, Intravenous; D007527:Isoenzymes / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D011451:Prostaglandin-Endoperoxide Synthases / Q000187:drug effects* / Q000378:metabolism; D013449:Sulfonamides / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000494:pharmacology*
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors; D007527:Isoenzymes; D013449:Sulfonamides; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; C012655:nimesulide