Effect of dipyrone, acetylsalicylic acid and acetaminophen on human neutrophil chemotaxis.

Dipyrone metabolites 4-methylaminoantipyrine (MAA) and 4-formylaminoantipyrine (FAA) as well as acetylsalicylic acid inhibited neutrophil migration toward zymosan-activated serum. Inhibition was maximal (76.8 +/- 19.0; 79.2 +/- 12.5 and 80.0 +/- 4.4%, respectively, P less than 0.003) when suboptimal concentrations (0.3%) of the chemoattractant were used and could be demonstrated with drug concentrations comparable with plasma concentrations obtained in clinical use. Acetaminophen and other dipyrone metabolites 4-aminoantipyrine (AA) and 4-acetylaminoantipyrine (AAA) lacked chemotactic inhibitory potential. Only MAA and FAA inhibited mildly neutrophil random migration (18.1 +/- 7.8 and 11.2 +/- 3.4%, respectively). We suggest that blocking neutrophil movement plays a role in the anti-inflammatory activity of dipyrone and acetylsalicylic acid, but their mechanism of inhibition remains obscure.