Objective—To evaluate the in vivo effects of firocoxib, meloxicam, and tepoxalin on prostaglandin (PG) and leukotriene production in duodenal mucosa and other target tissues in dogs with chronic osteoarthritis (OA).
Animals—8 dogs with chronic, unilateral OA of the stifle joint.
Procedures—In a crossover design, each dog received placebo (no treatment), firocoxib, meloxicam, or tepoxalin for 7 days, followed by a 21-day washout period. On the first day of treatment (day 0; baseline) and days 2, 4, and 7, samples of whole blood, synovial fluid, and gastric and duodenal mucosae were collected. Prostaglandin E2 concentrations were measured in synovial fluid of the stifle joint and after ex vivo stimulation of whole blood samples. Synthesis of PGE1 and PGE2 was measured in samples of gastric and duodenal mucosae. Concentrations of thromboxane B2 (TxB2) were measured in whole blood samples. Leukotriene B4 (LTB4) concentrations were measured in samples of whole blood (ex vivo stimulation) and gastric and duodenal mucosae.
Results—Firocoxib, meloxicam, and tepoxalin significantly suppressed whole blood concentrations of PGE2, compared with baseline and placebo concentrations, at days 2, 4, and 7. Tepoxalin significantly suppressed serum TxB2 concentrations, compared with baseline, firocoxib, meloxicam, and placebo, at all 3 time points. Production of PGE1 and PGE2 was significantly lower in duodenal versus gastric mucosa. Tepoxalin significantly decreased rates of PGE1 and PGE2 in duodenal and gastric mucosae, compared with baseline rates.
Conclusions and Clinical Relevance—PG production was lower in the duodenum than in the stomach. Firocoxib had a COX-1–sparing effect in vivo.