5-alpha-reductase inhibitors are a group of medicines that block the action of 5-alpha-reductase, the enzyme that converts testosterone into dihydrotestosterone. This results in increased levels of testosterone and decreased levels of dihydrotestosterone; an overabundance of dihydrotestosterone has been implicated in benign prostatic hyperplasia (BPH) and prostate cancer. The scalp of men with androgenetic alopecia (male-pattern baldness) has also been found to contain increased amounts of dihydrotestosterone and miniaturized hair follicles compared with men who have a lot of hair.
Currently, two 5-alpha-reductase inhibitors are available, finasteride and dutasteride. The 5-alpha-reductase enzyme exists in two forms: type 1 and type 2. Finasteride inhibits type 2 only, whereas dutasteride inhibits both. Although dutasteride provides greater suppression of dihydrotestosterone, it is not known if this provides a significant advantage clinically. Rates of side effects such as impotence, decreased libido, ejaculation disorder, and gynecomastia are similar.
5-alpha-reductase inhibitors may be used in the treatment of benign prostatic hyperplasia (enlarged prostate gland) and male-pattern hair loss (androgenic alopecia). They are not approved for the prevention of prostate cancer.
Dutasteride is used alone or with another medication (tamsulosin [Flomax]) to treat benign prostatic hyperplasia (BPH; enlargement of the prostate gland). Dutasteride is used to treat symptoms of BPH and may reduce the chance of developing acute urinary retention (sudden inability to urinate). Dutasteride may also decrease the chance that prostate surgery will be needed. Dutasteride is in a class of medications called 5-alpha reductase inhibitors. It works by blocking the production of a natural substance that enlarges the prostate.
Finasteride (Proscar) is used alone or in combination with another medication (doxazosin [Cardura]) to treat benign prostatic hypertrophy (BPH, enlargement of the prostate gland). Finasteride is used to treat symptoms of BPH such as frequent and difficult urination and may reduce the chance of acute urinary retention (sudden inability to urinate). It also may decrease the chance that prostate surgery will be needed. Finasteride (Propecia) is also used to treat male pattern hair loss (gradual thinning of the hair on the scalp, leading to a receding hairline or balding on the top of the head in men.) Finasteride (Propecia) has not been shown to treat thinning hair at the temples and is not used to treat hair loss in women or children. Finasteride is in a class of medications called 5-alpha reductase inhibitors. Finasteride treats BPH by blocking the body's production of a male hormone that causes the prostate to enlarge. Finasteride treats male pattern hair loss by blocking the body's production of a male hormone in the scalp that stops hair growth.
