The in vivo assessment of nimesulide cyclooxygenase-2 selectivity.

In man, nimesulide selectively inhibits cyclooxygenase-2 (COX-2) with little effect on haemostatic function or gastric prostaglandin formation. It causes significantly less gastrointestinal injury than naproxen, but has anti-inflammatory efficacy similar to that of naproxen and other currently available non-steroidal anti-inflammatory drugs. Naproxen suppressed arachidonic-acid-mediated platelet aggregation, reduced serum thromboxane B2 levels by 98% throughout the treatment period and reduced gastric mucosal prostaglandins (PGE2 and 6-keto-PGF1alpha) production by an average of 80%. This contrasts with nimesulide: platelet aggregation was not significantly affected, thromboxane B2 levels were only 29% lower and the gastric mucosal prostaglandins were inhibited in the order of approximately 20%. During the treatment period, both nimesulide and naproxen significantly inhibited COX-2-dependent PGE2 synthesis in the whole blood; however, naproxen had a lesser effect than nimesulide.