Mechanism of anti-inflammatory action of etodolac.

The effect of etodolac (CAS 41340-25-4) on the inflammatory reactions induced by histamine and bradykinin was compared with that of indomethacin and other nonsteroidal anti-inflammatory drugs. Etodolac (50 mg/kg p.o.), indomethacin (20 mg/kg p.o.), diclofenac Na (20 mg/kg p.o.) and acetylsalicylic acid (200 mg/kg p.o.) had no effect on the increase of vascular permeability induced by histamine or bradykinin and on passive cutaneous anaphylaxis in rats. Etodolac (5, 10 and 20 mg/kg p.o.) suppressed concanavalin A-induced paw edema in rats. Etodolac (10 mg/kg p.o.) and bromelain (10 mg/kg i.v.) significantly suppressed the heat-induced elevation of bradykinin in perfusates of rat paws, but indomethacin (20 mg/kg p.o.) and diclofenac Na (20 mg/kg p.o.) did not. Etodolac inhibited bradykinin-forming enzyme activity in a concentration-dependent manner (IC50 = 1.5 x 10-4) mol/l). These results suggest that etodolac is a unique nonsteroidal anti-inflammatory drug which can inhibit bradykinin formation, unlike indomethacin or diclofenac Na.