The Influence of Skin Structure on Permeability: An Intersite and Interspecies Comparison with Hydrophilic Penetrants

Topical finasteride may have higher systemic absorption and lower efficacy when using a Propylene Glycol/Ethanol formulation compared to the hydroxypropyl chitosan (HPCH) formulation. The safety profile of topical finasteride relies heavily on the HPCH formulation, and using standard solutions might lead to different pharmacokinetics.

The conversation discusses the potential benefits of creating a hydrophobic version of finasteride to reduce systemic side effects while maintaining scalp health. It compares this idea to fluridil, which is designed to be hydrophobic and has less systemic absorption.

The conversation discusses how the absorption rate of topical finasteride varies and is not equivalent to its oral form, with only a small percentage reaching the scalp. It also mentions that minoxidil in high concentrations is used topically because only a small amount is absorbed.

The conversation is about using distilled water as a solvent for topical finasteride to reduce systemic absorption. The user is considering avoiding ethanol and propylene glycol to achieve this.

Topical finasteride with hydroxypropyl chitosan shows significantly less serum absorption and minimal DHT reduction compared to oral finasteride. Users need the specific chitosan formulation to avoid side effects seen with regular ethanol+PG solutions.

The user mixes their own RU58841 solution and found that increasing the ethanol content improved absorption and reduced scalp itching. A study on minoxidil showed that penetration increased with higher ethanol concentrations, reaching maximum penetration at 90% ethanol.