Influence of vehicles on the phase transitions of model sebum.

It is hypothesized that vehicles that are miscible with sebum may concentrate drugs in the sebaceous follicle. This is important for the treatment of diseases like alopecia and acne. The main objective of the study was to identify different vehicles that affect the thermal behavior of sebum using differential scanning calorimetry (DSC). For this purpose, a model sebum mixture was prepared based on a composition reported in the literature. The test vehicle was added in a concentration of 15% of the weight of the sebum. Small portions of the above mixture were put in a pre-weighed DSC pan. These were run from -50 to 100 degrees C at 5 degrees C/minute. In the model sebum, four distinct transitions were observed: Mp-1 and Mp-2 occurred below 0 degrees C while Mp-3 and Mp-4 occurred above 30 degrees C. Vehicles that affected Mp-3 and Mp-4 were considered for further analysis. From the vehicles tested it was found that the hydrophobic materials were more effective in lowering Mp-3, while the ones that affected Mp-4 did not show any particular trend. Some of the vehicles tested are known skin permeation enhancers, and it is proposed that they interact with sebum and increase permeation by the follicular route. It was found that DSC may be used to identify vehicles that are miscible with sebum and that may deliver drugs preferentially to the sebaceous follicle.