Transfollicular Drug Delivery: Penetration of Drugs Through Human Scalp Skin and Comparison of Penetration Between Scalp and Abdominal Skins In Vitro

The study investigated drug penetration through human scalp skin using both lipophilic and hydrophilic drugs and compared it to penetration through abdominal skin. It found that lipophilic drugs like melatonin (MT) and ketoprofen (KP) had high permeability through scalp skin, with KP showing a much higher flux. Hydrophilic drugs like fluorouracil (5FU) and acyclovir (ACV) also penetrated the scalp skin with significant fluxes, but with considerable variability from different scalp sources. A positive correlation was observed between drug flux and hair follicle density. Histologic examination showed that drugs penetrated into the hair follicles and diffused into the dermis. The penetration of drugs through the scalp was significantly higher than through abdominal skin, with MT and 5FU being 27 and 48 times higher, respectively. This suggests that the scalp skin could be a viable route for drug delivery, especially for hydrophilic drugs.