Inhibitory effect of allopurinol on adjuvant arthritis in rats.

The effect of Allopurinol (ALLO), on adjuvant arthritis was studied in rats and compared with the effect of indomethacin (IND). Drugs were given by intraperitoneal injection for each day beginning from the day of adjuvant injection (day 0) and continued until the 16th day. Paw swelling was measured on days 4, 17 and 29, and secondary lesions were assessed on days 17 and 29. Polymorphonuclear leukocyte (PMNs) count was also evaluated on day 17. ALLO, at relatively high doses (25-50 mg/kg), reduced paw swelling of the adjuvant-injected extremity on day 4; lower doses (6.25-12.5 mg/kg), however, elicited the same inhibitory effect on day 17. IND (0.25 mg/kg) also prevented paw swelling on days 4 and 17. Both ALLO and IND reduced the secondary lesions on days 17 and 29 and prevented the increase in polymorphonuclear leukocytes during the development of adjuvant arthritis. Possible mechanisms of the antiinflammatory effect of ALLO in adjuvant arthritis are discussed.