Minoxidil Topical Treatment May Be More Efficient If Applied on Damp Scalp Compared to Dry Scalp

The study conducted by T. Angelo, G. N. Barbalho, G. M. Gelfuso & T. Gratieri in 2016 investigated the effectiveness of minoxidil, a topical treatment for androgenic alopecia, when applied on damp versus dry scalp. The researchers hypothesized that applying minoxidil on a damp scalp could lead to higher drug penetration, as humidity might favor drug diffusion into the hair follicle and prevent drug crystallization, maintaining a higher thermodynamic activity for longer periods. This hypothesis was confirmed through in vitro experiments on rat and porcine skin, showing that minoxidil follicular accumulation was about fivefold increased in towel-dried hair skin, compared to completely air-blown dried hair skin in rat experiments. The porcine experiments corroborated the results with eightfold increased follicular retention and higher skin deposition for towel-dried pieces. The study concluded that the state of scalp hydration during the application of minoxidil significantly influences the drug's permeation rate.