Modeling transdermal permeation. Part 2. Predicting the dermatopharmacokinetics of percutaneous solute

The prediction of percutaneous absorption and bioavailability in vivo, using the recently reported "bricks-and-mortar" model is discussed. Two sets of in vivo data have been simulated: the tape-striping data of 4-cyanophenol and Raman spectrometry data of transretinol. The predicted transdermal permeation using theoretically derived properties agreed well with the experimental data. The prediction shows that about 2/3 of the 4-cynophenol in the SC partitioned into the corneocytes, indicating diffusion of moderately hydrophobic solutes across the corneocytes is also important. Only for highly hydrophobic solute like transretinol, diffusion across the corneocytes is negligibly small. The study demonstrates that with the mechanism-based computer model, many dermatopharmacokinetic parameters can be derived, providing much insight into how vehicle formulation and topical administration affects the absorption and distribution of solute in the SC, as well as its bioavailability in epidermis/dermis. © 2010 American Institute of Chemical Engineers (AIChE)