EFFECT OF PIRPROFEN ON BRADYKININ-INDUCED FLEXOR REFLEXES OF RAT AND RABBIT HINDLIMBS

The analgesic effects of pirprofen on bradykinin-induced flexor reflexes in rats and rabbits were investigated in comparison with those of indomethacin and ibuprofen by oral administrations. The bradykinin-induced flexor reflexes in rats were suppressed by pirprofen at 10 mg/kg .apprx. 200 mg/kg, the effect reaching plateau at over 30 mg/kg. Suppression at the dose of 200 mg/kg was 56%. A similar dose-dependent curve was obtained for ibuprofen at 30 mg/kg .apprx. 300 mg/kg. On the other hand, indomethacin exerted dose-dependent inhibition at 1 mg/kg .apprx. 10 mg/kg without a tendency to reach the plateau effect within this dose range. Suppression at the dose of 10 mg/kg was 83%. The ED50 values of pirprofen, indomethacin and ibuprofen were 68 mg/kg, 3.3 mg/kg and 94 mg/kg, respectively. On the bradykinin-induced flexor reflexes in rabbits, pirprofen showed 60% suppression at the dose of 10 mg/kg, of which the effects were roughly equivalent to those of indomethacin and ibuprofen at the same dosage. These results indicate that there is a species difference concerning the three drug activities on bradykinin-induced flexor reflexes between the rat and the rabbit.