Inhibition of the late phase response to anti-IgE in humans by indomethacin.

The hypothesis of cyclooxygenase derivates of arachidonic acid as putative mediators of late phase skin reactions (LPR) was evaluated by studying the effect of indomethacin and naproxen on anti-IgE elicited skin reactions in healthy volunteers. Indomethacin 50 mg t.i.d., 48 h prior to and up to 24 h following challenge with anti-IgE 1/3300 (v/v), produced a slight attenuation of the flare response and a 35% inhibition of the LPR (P less than 0.05) at 1-24 h as compared with placebo (n = 11). Naproxen, 250 mg, b.i.d. showed analogous anti-LPR effect (n = 4, P less than 0.05). Intradermally (i.d.) injected indomethacin, 75 micrograms (7 X 10(-3) mol/l), attenuated the flare and LPR to anti-IgE 1/330 at 1-6 h (n = 12, P less than 0.01). Indomethacin, oral and i.d., enhanced the LPR to various dilutions of anti-IgE in 30% of the individuals. The results suggest that prostaglandins and thromboxanes participate in the development of an LPR in human skin.