Finasteride

Also known as: Propecia (1 mg brand), Proscar (5 mg brand), type II 5-alpha-reductase inhibitor

Hair Restore

In plain English

Finasteride is a medicine for male-pattern hair loss. It lowers the amount of a hormone called DHT, which is the main driver of hereditary thinning at the crown and hairline. Taken as a daily pill (or applied to the scalp in compounded forms), it works by protecting existing hairs and can help some regrowth, but it must be used continuously — the benefit fades within about a year of stopping. The FDA-approved product is the 1 mg oral tablet for men; compounded strengths and topical versions prepared by a pharmacy are not separately FDA-approved.

The science

Finasteride is a competitive inhibitor of type II 5-alpha-reductase, the enzyme that converts testosterone to the more potent androgen dihydrotestosterone (DHT). In androgenetic alopecia, DHT miniaturizes genetically susceptible scalp follicles; oral finasteride 1 mg/day lowers scalp and serum DHT and, in the pivotal 2-year randomized trials of 1,553 men, significantly increased vertex hair counts and slowed progression versus placebo. Topical finasteride can reduce scalp DHT with lower systemic exposure, but formulations are compounded and less standardized.

References

• Kaufman KD et al., J Am Acad Dermatol 1998
• Traish AM, Fertil Steril 2020 (post-finasteride syndrome review)
• Gray SL & Semla TP, BMJ 2019 (post-finasteride syndrome editorial)