Therapeutic effects of gel ointments containing tranilast nanoparticles on paw edema in adjuvant-induced arthritis rats.

Tranilast (TL), an antiallergic agent, has been clinically used in the treatment of bronchial asthma, although its clinical use has been limited by its poor solubility in water, photodegradation and systemic side effects. In this study, we prepared a gel ointment containing TL nanoparticles (TLnano gel ointment), and investigated its usefulness. In addition, we demonstrated the preventive effects of the TLnano gel ointment on inflammation in adjuvant-induced arthritis (AA) rats. The TLnano gel ointment was prepared using Bead Smash 12 (a bead mill) and additives including sodium docusate, 2-hydroxypropyl-β-cyclodextrin, methylcellulose and Carbopol 934; the mean particle diameter of the TL nanoparticles was 71.0±25.4 nm. In in vitro skin penetration experiments, the amount of penetrated TL, the penetration rate (Jc) and the penetration coefficient through the skin (Kp) of the TLnano gel ointment were significantly higher than those of a gel ointment containing TL microparticles (TLmicro gel ointment; particle diameter 50.5±26.3 µm). The TL concentrations in the skin tissue and plasma of rats receiving the TLnano gel ointment were also higher than in rats receiving the TLmicro gel ointment. In addition, the application of the TLnano gel ointment attenuated the increase in paw edema of the hind feet of AA rats in comparison with AA rats treated with the TLmicro gel ointment. These results suggest that TL nanoparticles can be applied to the formulation of a transdermal system, and that a transdermal formulation using TL nanoparticles might be a delivery option for the clinical treatment of RA.