The effect of timegadine, a novel experimental antirheumatic drug, on human neutrophil (PMN) 5-lipoxygenase activity and leukotriene B4 (LTB4) chemotaxis was compared with that of two second-line antiinflammatory drugs, D-penicillamine and levamisole. 1-14C-Arachidonic acid (AA) was incorporated into the purified cells until steady state conditions were obtained. After preincubation with serial dilutions of the three drugs, AA release and metabolism was stimulated with calcium ionophore A23187. The radioactive eicosanoids released were extracted and separated by thin-layer chromatography, followed by autoradiography and quantitative laser densitometry. Chemotaxis of PMNs towards LTB4 was measured in a modified Boyden chamber. Timegadine showed dose-dependent inhibition of both the 5-lipoxygenase pathway (IC50 3.4 x 10(-5) M), and of chemotaxis (IC50 3 x 10(-4) M). Inhibition of the release of AA from phospholipids, however, occurred only at therapeutically irrelevant doses (millimolar concentrations). Levamisole and D-penicillamine did not inhibit any of the cell functions investigated. Inhibition of both neutrophil motility and cellular synthesis of pro-inflammatory eicosanoids, may thus contribute to the clinical effects of timegadine in rheumatoid arthritis.