Evidence‑Based Aspects of 5‑Alpha‑Reductase Inhibitors in Frontal Fibrosing Alopecia

Mechanism of Action

5‑Alpha‑reductase inhibitors block the enzymatic conversion of testosterone to the more potent androgen dihydrotestosterone (DHT), thereby modulating the hormonal environment that contributes to the inflammatory scarring process in frontal fibrosing alopecia (FFA). [1][2]

Dutasteride inhibits both type 1 and type 2 isoforms of 5‑alpha‑reductase, achieving a more complete and consistent reduction of DHT than finasteride, which selectively blocks only the type 2 isoform. This broader inhibition underlies dutasteride’s superior efficacy in FFA treatment. [1][2]
Finasteride’s inhibition of only the type 2 isoform results in incomplete DHT suppression, which may translate into lower clinical efficacy for FFA compared with dutasteride. 1

In men, finasteride is associated with a 2–4 % higher incidence of sexual dysfunction—including erectile dysfunction, decreased libido, and ejaculatory disorders—relative to placebo, as demonstrated in placebo‑controlled randomized trials (high‑level evidence). [3][4]