Effects of glycerol on the in vitro percutaneous absorption of all-trans retinoic acid.

The nature of the receptor solution plays an important role in in vitro percutaneous absorption of highly lipophilic compounds having limited solubility. In vitro permeation studies of a lipophilic compound, all-trans retinoic acid (RA), through the rat dorsal skin were performed with the presence of glycerol (0-20% v/v) in the receptor solution, and the results were compared with those with the presence of albumin (4%). The results showed that an addition of glycerol (20%) into the receptor solution significantly increased the permeation rate of RA through the rat dorsal skin (0.0068 +/- 0.0041 vs. 0.0014 +/- 0.0010 microg/cm2/hr). It was also found that RA tends to accumulate in the lipophilic layer, and its log P value between the epidermis and the receptor solution significantly decreased with the presence of glycerol (20%) (1.48 +/- 0.14 vs. 2.45 +/- 0.21). An addition of glycerol, an osmotherapeutic agent, in the physiological receptor solution seemed to enhance the percutaneous absorption of RA by affecting the partition coefficient of RA.