We previously reported that dermal application using nanoparticles improves skin penetration. In this study, we prepared novel topical formulations containing ketoprofen (KET) solid nanoparticles (KET nano gel ointment) and investigated the antiinflammatory effect of the KET nanoparticle formulations on rheumatoid arthritis using adjuvant-induced arthritis (AA) rats. The KET nano gel ointment was prepared using a bead mill method and additives including methylcellulose and Carbopol 934; the mean particle size of the KET nanoparticles was 83 nm. In the in vitro skin penetration experiment, the penetration rate (J c ) and penetration coefficient through the skin (K p ) values of the KET nano gel ointment were significantly higher than those of gel ointment containing KET microparticles (KET micro gel ointment; mean particle size 7.7 µm). On the other hand, in the in vivo percutaneous absorption experiment, the apparent absorption rate constant (k a ) and the areas under the KET concentration-time curve values in the skin of rats receiving the KET nano gel ointment were significantly higher than those of rats receiving the KET micro gel ointment, and the amounts of KET in the skin tissues of rats receiving the KET nano gel ointment were also significantly higher than those of rats receiving the KET micro gel ointment. In addition, the application of the KET nano gel ointment attenuated the enhancement of paw edema of the hind feet of AA rats more than the application of the KET micro gel ointment. Our findings suggest that a topical drug delivery system using nanoparticles could lead to expansion in the therapeutic use of KET.Key words nanoparticle; ketoprofen; gel ointment; drug delivery; adjuvant-induced arthritis Ketoprofen (KET) is a reversible inhibitor of cyclooxygenases 1 and 2 whose action leads to a reduction in the formation of prostaglandin precursors. 1) Thus, KET acts as an antiinflammatory agent, and is used in the treatment of rheumatoid arthritis (RA) and osteoarthritis. However, its usefulness is limited due to its low water solubility and the fact that oral administration of KET tends to cause gastrointestinal lesions in 10-30% of patients. These gastrointestinal lesions lead to an interruption of drug therapy in about 5-15% patients. 2,3)Topical and transdermal delivery routes of drug administration reduce the incidence of gastrointestinal lesions and improve patient compliance. Furthermore, the transdermal route of application avoids hepatic first pass metabolism, meaning that therapeutic serum drug concentrations can be applied with a reduced risk of nephrotoxicity and drug-drug interactions.2) However, the transdermal route of application is limited by the barrier properties of the skin. Therefore, it is necessary to develop enhancement techniques to assist the skin penetration of KET, and extensive research has been done to find both topical and transdermal KET formulations.

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It was reported that cilostazol (CLZ) suppressed disruption of the microvasculature in ischemic areas. In this study, we have designed novel injection formulations containing CLZ nanoparticles using 0.5% methylcellulose, 0.2% docusate sodium salt, and mill methods (CLZnano dispersion; particle size 81 ± 59 nm, mean ± S.D.), and investigated their toxicity and usefulness in a cerebral ischemia/reperfusion-induced injury model (MCAO/reperfusion mice). The pharmacokinetics of injections of CLZnano dispersions is similar to that of CLZ solutions prepared with 2-hydroxypropyl-β-cyclodextrin, and no changes in the rate of hemolysis of rabbit red blood cells, a model of cell injury, were observed with CLZnano dispersions. In addition, the intravenous injection of 0.6 mg/kg CLZnano dispersions does not affect the blood pressure and blood flow, and the 0.6 mg/kg CLZnano dispersions ameliorate neurological deficits and ischemic stroke in MCAO/reperfusion mice. It is possible that the CLZnano dispersions will provide effective therapy for ischemic stroke patients, and that injection preparations of lipophilic drugs containing drug nanoparticles expand their therapeutic usage.

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