Effect of UV-absorbing agents on photodegradation of tranilast in oily gels

Tranilast (TL) oily gels containing UV-absorbing agents (UV absorber) were prepared. and the effect of the agents against photodegradation of TL was i nvestigated. When 0.1% TL oily gel without UV absorber was exposed to light , TL was photochemically decomposed to the extent of 74.1% of its initial c ontent at the end of the first hour. Although there were differences in the preventive effect on photodegradation of TL depending on the UV absorbers employed, 2-(2-benzotriazolyl)-p-cresol (BTPC) was the most effective absor ber. The addition of UV absorbers to the oily gel did not affect the releas e of TL from the gel, the skin permeation, or the skin concentration of TL following topical application. UV absorbers added to TL oily gel penetrated into skin; however, their concentration in skin was similar to that follow ing application of commercial sunscreen. These results suggest that the add ition of UV absorbers to the oily gel of TL may be useful in preventing pho todegradation of TL in the gel.