The protective value of piroxicam on the enhanced inflammatory response after whole body irradiation.

The anti-inflammatory activity of piroxicam was assessed after whole body irradiation in rats. Two models of inflammation, the carrageenan-induced oedema and the adjuvant-induced arthritis in rats have been utilised. Piroxicam at doses of 1, 5 & 10 mg kg-1 i.p. was effective in inhibiting the paw oedema produced in both models of inflammation. The inflammatory response in irradiated was significantly higher than that produced in normal animals and was dependent on the radiation dose level used (0.5-2 Gy). The effect of piroxicam on the late inflammatory response produced by exposure to 2 Gy was studied by measuring the carrageenan-induced oedema 4 h after irradiation and on the third and seventh day thereafter. The increase in paw volume was significantly suppressed in animals receiving the drug. Administration of piroxicam (5 mg kg-1) one hour before irradiation of animals at 0.5 Gy, produced inhibition to the exaggerated inflammatory response in irradiated animals. This suggests that piroxicam possibly owes its protective value to prevention of the increase in cellular permeability induced by radiation. Alternatively, the drug may exert this effect by inhibiting PG synthesis, thereby reducing their potentiating influence on the other mediators of inflammation. Furthermore, the inhibition of lysosomal enzyme release possibly induced by the drug may contribute to the probable reduction in the release of inflammatory mediators.