A comparison of the effects of nabumetone vs meloxicam on serum thromboxane B2 and platelet function in healthy volunteers

Aims  To compare the effects of nabumetone and meloxicam, two cyclo-oxygenase-2 (COX-2) preferential nonsteroidal anti-inflammatory drugs (NSAIDs), on platelet COX-1 activity and platelet function. Methods  Twelve healthy volunteers (3 male, 9 female, median age 22 years) participated in an open, randomized, cross-over trial of nabumetone 1000 mg twice daily vs meloxicam 7.5 mg twice daily during 1 week with 2 weeks wash-out. After a second 2 week wash-out period, one dose of indomethacin 50 mg was given as a positive control to check for NSAID induced inhibition of platelet function. COX-1 inhibition was measured as percentage inhibition of serum TXB2 generation in clotting whole blood, and as closure time with use of the platelet function analyser PFA-100. Data are reported as median with range. Paired variables were analysed using Wilcoxons signed rank test. Results  TXB2 levels decreased significantly after all three medications, but percentage inhibition after nabumetone and indomethacin (88% and 97%, respectively) was significantly higher than after meloxicam (63%) (P<0.05). Closure times increased significantly after administration of all three medications (P<0.05). Increases in closure time after administration did not differ between nabumetone and meloxicam (24% and 14%, respectively), but were significantly larger after indomethacin administration (63%) (P<0.01). Conclusions  In the maximum registered dosage, nabumetone inhibits thromboxane production much more than meloxicam, signifying less COX-2 selectivity of the former. However, both nabumetone and meloxicam cause only minor impairment in platelet function in comparison with indomethacin and the difference between them is not significant.