Finasteride does not completely suppress DHT production because it lacks significant inhibitory effects on the 5α-reductase type I isoenzyme, with more than 100-fold less inhibitory potency for type I as compared to type II (IC50 = 313 nM and 11 nM, respectively). This is in contrast to inhibitors of all three isoenzymes of 5α-reductase like dutasteride, which can reduce DHT levels in the entire body by more than 99%. In addition to inhibiting 5α-reductase, finasteride has also been found to competitively inhibit 5β-reductase (AKR1D1). However, its affinity for the enzyme is substantially less than for 5α-reductase (an order of magnitude less than for 5α-reductase type I) and hence is unlikely to be of clinical significance.As of 2012, the tissues in which the different isozymes of 5α-reductase are expressed are not fully clear. This is because different investigators have obtained varying results with different reagents, methods, and tissues examined. However, the different isozymes of 5α-reductase appear to be widely expressed, with notable tissues including the prostate gland, seminal vesicles, testes, epididymides, skin, hair follicles, liver, kidneys, and brain, among others.By inhibiting 5α-reductase and thus preventing DHT production, finasteride reduces androgen signaling in tissues like the prostate gland and the scalp. In the prostate, this reduces prostate volume, which improves BPH and reduces risk of prostate cancer. Finasteride reduces prostate volume by 20 to 30% in men with benign prostatic hyperplasia.
Finasteride, sold under the brand names Proscar and Propecia among others, is a medication used to treat hair loss and benign prostatic hyperplasia in men. It can also be used to treat excessive hair growth in women and as a part of hormone therapy for transgender women. It is taken by mouth.Finasteride is a 5α-reductase inhibitor and therefore an antiandrogen. It works by decreasing the production of dihydrotestosterone (DHT) by about 70%, including in the prostate gland and the scalp.In addition to DHT, finasteride also inhibits the production of several anticonvulsant neurosteroids including allopregnanolone, androstanediol and THDOC.Adverse effects from finasteride are rare, however some men experience sexual dysfunction, depression, and breast enlargement. In some men, sexual dysfunction may persist after stopping the medication. It may also hide the early symptoms of certain forms of prostate cancer.Finasteride was patented in 1984 and approved for medical use in 1992. It is available as a generic medication. In 2019, it was the 86th most commonly prescribed medication in the United States, with more than 8 million prescriptions. Medical uses
Finasteride is indicated for the treatment of symptomatic benign prostatic hyperplasia (BPH) in men with an enlarged prostate and for the treatment of male pattern hair loss (androgenetic alopecia) in men. Enlarged prostate
Physicians sometimes prescribe finasteride for the treatment of benign prostatic hyperplasia (BPH), informally known as an enlarged prostate.