Inhibition of prostaglandin biosynthesis by tolfenamic acid in vitro

The effect of tolfenamic acid on prostaglandin biosynthesis was investigated by using rabbit kidney medulla microsomal fraction, and the results compared with those obtained with indomethacin and acetylsalicylic acid. Tolfenamic acid inhibited the conversion of arachidonic acid to prostaglandin E2 very effectively and in a dose-dependent manner. IC50 values were 0.64 muM for tolfenamic acid, 0.76 muM for indomethacin, and 7 mM for acetylsalicylic acid. The inhibition of prostaglandin biosynthesis may be related to the good anti-inflammatory action of tolfenamic acid.