Selective local anti-inflammatory activity of THS-201, a new intra-articular steroid, in cotton pellet granuloma and monoarticular arthritis.

A new steroid, THS-201 was administered locally in one of a pair of inflamed sites and its local anti-inflammatory activity was compared with those of triamcinolone acetonide, methylprednisolone acetate and hydrocortisone acetate. In rats, THS-201 (80 micrograms/pellet) completely inhibited the formation of granulation tissue even after 21 days. In antigen-induced bilaterally arthritic rabbits, THS-201 (2 mg/joint) decreased the swelling of the treated knee joint for more than 24 days, but no such effect was seen in the opposite knee joint. The anti-inflammatory activity of the other steroids employed as reference drugs were weaker than that of THS-201. These results indicate that THS-201 is an anti-inflammatory steroids exclusively acting at the site of administration for a long period, and for this reason it might be suitable for intraarticular application in clinical use.