Finasteride
Type II 5-alpha reductase inhibitor; reduces DHT conversion
Mechanism of Action
Finasteride is a competitive inhibitor of type II 5-alpha-reductase (5AR), the enzyme that converts testosterone to dihydrotestosterone (DHT). By inhibiting 5AR type II (primarily expressed in prostate, hair follicles, and liver), finasteride reduces DHT levels by approximately 70%. Type I 5AR (expressed in skin and brain) is not significantly affected. Reduced DHT results in decreased androgenic stimulation of target tissues, studied for androgenic alopecia, benign prostatic hyperplasia, and as an adjunct during androgen administration to mitigate DHT-mediated side effects.
Evidence Level
Clinical Trial - Human
6 studies published
Studied For
Pharmacology
Molecular Weight
372.6 g/mol
Half-Life
Approximately 6-8 hours (oral); biological effects persist 24+ hours
Bioavailability
Approximately 80% oral bioavailability