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 μg/ml, 30 μg/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.