Penetration of naproxen and salicylate into inflammatory exudates in the rat.

Acute inflammation was induced in rats by subcutaneous implantation of plastic sponges, and the penetration of salicylate and naproxen into the inflammatory exudate was studied after oral dosing with these compounds. The penetration of intravenously administered 22Na and 125I-albumin was also studied. It was found that salicylate and 22Na penetrated very rapidly, reaching maximum concentration in the exudate within 3 hours of administration. In contrast, naproxen and 125I-albumin penetrated much more slowly, maximum concentrations in the exudates not being reached until 5 hours after administration. The significance of these results and the role of protein binding is discussed.