Percutaneous absorption of drug from alpha-olefin oligomer gel bases

The percutaneous absorption of drug from the alpha-olefin oligomer (alpha-OL) gel base prepared by using palmitate of dextrin (Rheopearl KL) as a gelling agent was investigated by using the abdominal skin of rats in vivo. The 20, 30, 40 and 50 alpha-OLs with average molecular weights of 288, 380, 440 and 535, respectively were used in this study. The flurbiprofen (FP) was selected as a model drug. The percutaneous absorption of FP from the alpha-OL gel base was observed to be influenced by the molecular weight of alpha-OL. The percutaneous absorption profiles of FP from 40 and 50 alpha-OLs gel bases were almost the same. On the other hand, the absorption of FP from 30 alpha-OL gel base was significantly higher than those of 40 and 50 alpha-OLs gel bases. Furthermore, the percutaneous absorption of FP from 20 alpha-OL gel base was observed to be the highest in the test gel bases. In order to establish the reason for the differences in the percutaneous absorption of FP from 20, 30, 40 and 50 alpha-OLs gel bases, the apparent partition ratios of FP between water and four different alpha-OLs were determined as a parameter of the affinity of FP for the vehicle. Consequently, it has become apparent that the partition ratio exerts an influence on the percutaneous absorption of FP from the alpha-OL gel bases.