The in vivo assessment of nimesulide cyclooxygenase-2 selectivity

In man, nimesulide selectively inhibits cyclooxygenase-2 (COX-2) with littl e effect on haemostatic function or gastric prostaglandin formation. It cau ses significantly less gastrointestinal injury than naproxen, but has anti- inflammatory efficacy similar to that of naproxen and other currently avail able non-steroidal anti-inflammatory drugs. Naproxen suppressed arachidonic -acid-mediated platelet aggregation, reduced serum thromboxane B-2 levels b y 98% throughout the treatment period and reduced gastric mucosal prostagla ndins (PGE(2) and 6-keto-PGF(1 alpha)) production by an average of 80%. Thi s contrasts with nimesulide: platelet aggregation was not significantly aff ected, thromboxane B-2 levels were only 29% lower and the gastric mucosal p rostaglandins were inhibited in the order of similar to 20%. During the tre atment period, both nimesulide and naproxen significantly inhibited COX-2-d ependent PGE(2) synthesis in the whole blood; however, naproxen had a lesse r effect than nimesulide.