The objective of this study was to determine the effects of orally administered misoprostol and diclofenac on inflammation caused by particulates in the rat subcutaneous air-pouch model. Subcutaneous air pouches were formed in male Sprague-Dawley rats. The animals were premedicated by gavage with either saline, diclofenac, misoprostol, or both diclofenac and misoprostol. The air pouches were injected with either polymethyl methacrylate particles or monosodium urate crystals, and the pouch fluids were obtained at 1, 6, 24, 48, and 72 h. Leukocyte influx, tumor necrosis factor, neutral metalloprotease activity, and prostaglandin E(2) levels were measured. It was determined that leukocyte influx was inhibited by diclofenac in the acute inflammation caused by monosodium urate crystals only. In all animals receiving diclofenac, prostaglandin E(2) (PGE(2)) levels were reduced, whereas tumor necrosis factor levels were elevated. The elevation of tumor necrosis factor was prevented by the addition of misoprostol. It is concluded that the oral administration of diclofenac or misoprostol can affect levels of specific mediators involved in particulate-induced inflammation in the subcutaneous air pouch.