Transdermal finasteride delivery via powder-carrying microneedles with a diffusion enhancer to treat androgenetic alopecia.

Androgenetic alopecia is a common form of scalp hair loss that affects men in their mid-twenties and increases with age. Finasteride (FNS) has been approved and used orally to treat androgenetic alopecia; however, systemic effects on other androgen-dependent tissues cause severe side-effects. To overcome these systemic effects and target hair follicles in the scalp only, numerous topical formulations of FNS have been developed and further combined with the solid microneedle (SMN) technique to create micro-channels in the skin, thus overcoming the skin barrier properties. However, low delivery efficiency and concerns over patient safety of SMNs remain major limitations of the treatment. In the present study, we developed a novel FNS delivery system comprising powder-carrying microneedles (PCMs), which is a patch-less and self-administered powder delivery technique that simultaneously overcomes the safety issues. This system could directly implant FNS inside the skin by encapsulating the FNS powder in the center of the PCMs. In addition, we introduced the concept of a diffusion enhancer for this system, which facilitated the dissolution and release of the implanted FNS powder to achieve its successful intradermal delivery. Using implanted FNS powder as a reservoir inside the skin, this novel system permitted sustained release of the implanted FNS powder for 3 days with only one application of FNS-PCMs. In addition, compared with the topical FNS-gel, the developed system showed a higher efficacy in promoting hair growth and increased the amount and density of hair while addressing the safety concerns. This approach has the potential to advance the field of transdermal drug delivery for any type of powdered drug in a wide variety of biomedical applications.