Tramadol anti-inflammatory activity is not related to a direct inhibitory action on prostaglandin endoperoxide synthases

The analgesic drug tramadol has been shown to relieve pain in inflammatory; conditions, to inhibit the development of experimental inflammation, and to reduce prostaglandin (PG)E-2 concentrations in the inflammatory exudate. In this study, we evaluated the putative activity of tramadol to suppress prostaglandin endoperoxide synthase-1 (PGHS-1), and prostaglandin endoperoxide synthase-2 (PGHS-2) activities in human whole blood in vitro. Platelet thromboxane (Tx)B-2 production and monocyte PGE(2) production in LPS-stimulated blood were measured in samples incubated with different concentrations (300 ng/ml, 3 mug/ml, 30 mug/ml) of tramadol or its enantiomers Neither tramadol nor the enantiomers inhibited the formation of arachidonic acid metabolites. Our results indicate that the anti-inflammatory effect of tramadol demonstrated in some models is not related to a direct inhibitory effect on the formation of prostanoids. (C) 2000 European Federation of Chapters of the International Association for the Study of Pain.