Finasteride

Finasteride, sold under the brand names Proscar and Propecia among others, is a medication used to treat pattern hair loss and benign prostatic hyperplasia (BPH). It can also be used to treat excessive hair growth in women. It is usually taken orally but there are topical formulations for patients with hair loss, designed to minimize systemic exposure by act

Finasteride, sold under the brand names Proscar and Propecia among others, is a medication used to treat pattern hair loss and benign prostatic hyperplasia (BPH).[6] It can also be used to treat excessive hair growth in women.[7] It is usually taken orally but there are topical formulations for patients with hair loss, designed to minimize systemic exposure by acting specifically on hair follicles.[8]

Finasteride is a 5α-reductase inhibitor and therefore an antiandrogen.[9] It works by decreasing the production of dihydrotestosterone (DHT) by about 70%.[6]

In addition to DHT, finasteride also inhibits the production of several anticonvulsant neurosteroids including allopregnanolone, androstanediol, and tetrahydrodeoxycorticosterone.[10]

Adverse effects from finasteride are rare in men with already enlarged prostates;[11] however, some men experience sexual dysfunction, depression, and breast enlargement.[12][13] In some men, sexual dysfunction may persist after stopping the medication.[14][15] It may also hide the early symptoms of certain forms of prostate cancer.[13]

Finasteride was patented in 1984 and approved for medical use in 1992.[16] It is available as a generic medication.[17] In 2023, it was the 91st most commonly prescribed medication in the United States, with more than 7 million prescriptions.[18][19]

Medical uses

Finasteride has been used for the treatment of symptomatic benign prostatic hyperplasia (BPH)[3] and for the treatment of male pattern hair loss.[4]

Enlarged prostate

Physicians sometimes prescribe finasteride for the treatment of benign prostatic hyperplasia, informally known as an enlarged prostate.[20] Finasteride may improve the symptoms associated with BPH such as difficulty urinating, getting up during the night to urinate, hesitation at the start and end of urination, and decreased urinary flow.[21]

The use of the drug showed significant sexual adverse effects such as erectile dysfunction and less sexual desire, in particular when obstructive symptoms due to an enlarged prostate were present.[22]

Pattern hair loss

Finasteride is also used to treat male pattern baldness (androgenic alopecia), a condition that develops in up to 80% of Caucasian men aged 70 and over.[23][4] In the United States, finasteride and minoxidil are the only two FDA-approved drugs for the treatment of male pattern hair loss as of 2017.[24] Treatment with finasteride slows further hair loss.[25] Two meta-analyses[26][27] found finasteride's efficacy caused about 15% hair regrowth. Specifically oral finasteride was observed to regrow about 18 hair follicles in a square centimeter area of scalp. In comparison a full head of hair usually has 120 hair follicles per square centimeter scalp.[28]

Taking finasteride leads to a reduction in scalp and serum DHT levels; by lowering scalp levels of DHT, finasteride can maintain or increase the amount of terminal hairs in the anagen phase by inhibiting and sometimes reversing miniaturization of the hair follicle. Finasteride is most effective on the crown but can reduce hair loss in all areas of the scalp.[29][30] Finasteride has also been tested for pattern hair loss in women; however, the results were no better than placebo.[31] Finasteride is less effective in the treatment of scalp hair loss than dutasteride.[32][33]

Prostate cancer

In males aged 55 years old and over finasteride decreases the risk of low-grade prostate cancer but may increase the risk of high-grade prostate cancer and has no effect on overall survival.[34]

A 2010 review found a 25% reduction in the risk of prostate cancer with 5α-reductase inhibitor.[35] A follow-up study of the Medicare claims of participants in a 10-year Prostate Cancer Prevention Trial suggests the reduction in prostate cancer is maintained even after discontinuation of treatment.[36] However, 5α-reductase inhibitors have been found to increase the risk of developing certain rare but aggressive forms of prostate cancer (27% risk increase), although not all studies have observed this.[37] No impact of 5-α-reductase inhibitor on survival has been found in people with prostate cancer.[37]

Excessive hair growth

Finasteride has been found to be effective in the treatment of hirsutism (excessive facial or body hair growth) in women. In a study of 89 women with hyperandrogenism due to persistent adrenarche syndrome, finasteride produced a 93% reduction in facial hirsutism and a 73% reduction of bodily hirsutism after 2 years of treatment. Other studies using finasteride for hirsutism have also found it to be effective.[7]

Transgender hormone therapy

Finasteride is sometimes used as an antiandrogen in feminizing hormone therapy for transfeminine people.[38] There are limited clinical data on finasteride for this use and some authorities explicitly recommend against its routine use.[39][40][41][42] Relatedly, the medication is considered to be limitedly useful and unnecessary in transfeminine people with testosterone levels in the normal female range.[39][41][40][43] However, finasteride may be helpful in those with higher testosterone levels and symptoms like scalp hair loss and excessive body hair or who seek only partial feminization.[43][38][44]

Besides transfeminine people, finasteride is helpful in transmasculine people for preventing scalp hair loss and is better-established for this purpose, though it might impede masculinization such as clitoral growth and development of facial and body hair.[44][39][41][38]