Indomethacin is a competitive inhibitor of the binding of the chemotactic peptide formyl-Met-Leu-Phe to human polymorphonuclear leukocytes.

Indomethacin, a non-steroidal anti-inflammatory drug, competes with the tritiated chemotactic peptide formyl-Met-Leu-Phe (FMLP) for binding to human neutrophils (PMN). This competition which occurs in the concentration range 10(-6)-10(-3) M, with an IC50 of 7 x 10(-5) M, is inversely proportional to the concentration of albumin present in the incubation medium. These data explain why indomethacin is able to inhibit, in the same concentration range and with the same IC50, many of the physiological responses of PMN elicited by the chemotactic peptide formyl-Met-Leu-Phe.