The pharmacokinetic properties and antiinflammatory activity of 3% ketoprofen lotion (ID-lotion), formulated with poloxamer 407, were evaluated using rats. For the pharmacokinetic study, the lotion, at the dose of 4.5 mg/kg, was applied on the dorsal skin of rats and the drug concentration in plasma was determined using an HPLC method. As references, ketoprofen suspended in saline was administered orally, and Elotion, which is a 3% ketoprofen lotion in the Japanese market, was applied transdermally. Following the transdermal application of ID-lotion and E-lotion, C_(max) were 316±22.3 ng/ml and 163 ±12.2 ng/ml, respectively, at the same T_(max) of 2 hours postdose, while C_(max) and T_(max) after oral administration of the drug were 1,030 ±89.1 ng/ml and 0.25 hours, respectively. Relative bioavailabilities of ID-lotion and E-lotion were 69.3% and 34.2%, respectively. The antiinflammatory activity of the two 3% ketoprofen lotions was evaluated with carrageenen-induced edema method after 50 mg of the lotions was applied on the paw of rats. ID-lotion showed 67.6% inhibition of the edema formation, while E-lotion showed 34.7%. The calculated EDT after transdermal application of ID-lotion was 2.5 mg/kg, while that after oral administration was 7.0 mg/kg. Based on these results, the relative equiponderal availability of ID-lotion was 296% compared to the oral administration of ketoprofen.