Tolfenamic acid inhibits leukotriene B4-induced chemotaxis of polymorphonuclear leukocytes in vitro.

Inhibition of prostanoid synthesis is usually regarded as the mode of action of nonsteroidal antiinflammatory drugs (NSAIDs). In addition, some NSAIDs have been reported to have prostanoid-independent inhibitory effects on neutrophil functions. In the present study, we examined the effects of acetylsalicylic acid, diclofenac, indomethacin, ketoprofen, piroxicam and tolfenamic acid on leukotriene B4 (LTB4)-induced chemotaxis of human polymorphonuclear leukocytes (PMNs) in vitro. Tolfenamic acid inhibited LTB4-induced chemotaxis (IC50 59 microM), whereas the other compounds were ineffective. Tolfenamic acid inhibited also FMLP-induced chemotaxis at the same concentration range (IC50 46 microM). About 25% reduction in the chemotactic response was achieved with therapeutic concentrations of tolfenamic acid. We suggest that the inhibition of PMN chemotaxis is an additional mechanism in the antiinflammatory action of tolfenamic acid and that this action is not ligand specific.