The mechanism of action of sulfapyridine in RA has not been identified [7]. Since sulfapyridine is a sulfonamide, an antibacterial effect has been entertained; however, the observation that other sulfonamides are ineffective in RA makes this hypothesis unlikely. One 24-week study, for example, directly compared sulfapyridine (1.25 gram per day) with cotrimoxazole (trimethoprim-sulfamethoxazole, 480 mg three times daily) in patients with RA [12]. Disease activity either was unchanged or had worsened among patients treated with cotrimoxazole; by comparison, improvement was observed in those administered sulfapyridine. Sulfapyridine may also reduce secretions of inflammatory cytokines such as interleukin (IL)-8 and monocyte chemoattractant protein (MCP)-1 [11].