Abstract
The effects of two kinds of fatty acids (stearic acid and palmitic acid) added to mixture of fatty alcohol and propylene glycol (FAPG base) on the percutaneous absorption of indomethacin (ID) were investigated by using the normal abdominal skin of rats in vivo. The percutaneous absorption of propylene glycol (PG) from FAPG base was simultaneously examined.
The percutaneous absorption profiles of ID from No. 1 (consisting of stearyl alcohol and 75% PG) and from No. 2 (consisting of stearyl alcohol, stearic acid and 75% PG) bases were almost the same. On the other hand, the absorption of ID from No. 3 base (consisting of stearyl alcohol, palmitic acid and 75% PG) was significantly higher than those from Nos. 1 and 2 bases. Furthermore, PG was readily absorbed through the rat skin from Nos. 1, 2 and 3 FAPG bases and its percutaneous absorption profiles were similar to those of ID.
In order to establish the reason for the differences in percutaneous absorption of ID from the three bases, the apparent partition ratio of ID between water and vehicle was determined as a parameter of the affinity of ID for the vehicle. There was no difference in apparent partition ratio between Nos. 1 and 2 bases, while that of No. 3 base was the highest among the vehicles tested. The release of ID from Nos. 1, 2 and 3 bases in vitro was also studied by using a silicone rubber membrane. The results of the in vivo test were broadly consistent with those of the in vitro tests.
