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Finasteride (brand name Propecia®) is an orally administered medication for male pattern hair loss (MPHL). It is the only specific MPHL treatment approved by the U.S. Food and Drug Administration for prescription by a physician. Several years of investigation and use by more than a million patients show that finasteride has long-term effectiveness and safety in treating MPHL in men of all ages and all ethnic backgrounds. Finasteride is sometimes used alone or in combination with minoxidil (see Using Minoxidil (Rogaine)) to complement hair transplantation. Finasteride is not recommended for use in women.

Finasteride’s effects in slowing hair loss and stimulating new hair growth work best for early to moderate degrees of hair loss. Men with extensive hair loss are unlikely to experience much regrowth with finasteride; these men are better candidates for hair transplantation or other surgical approach to hair restoration.

Finasteride is most effective in stimulating hair regrowth over the crown of the scalp. It is less effective in stimulating regrowth at the front of the scalp-where hair loss is commonly called a “receding hairline”. Physician hair restoration specialists may prescribe finasteride to prevent further hair loss by the patient, and carry out hair transplantation to provide coverage at the frontal hairline.

Finasteride: How It Works

Finasteride works at the molecular level to halt hair loss and stimulate new hair growth. It is a medication that selectively inhibits the activity of an enzyme that converts the “male hormone” testosterone into a form that is active in hair follicles.

Androgenic (“male”) hormones such as testosterone have multiple effects in the body, including actions in the skin, hair follicles and prostate gland. Hair follicles and sebaceous (oil-producing) glands in the skin are particularly responsive to androgenic hormones.

Testosterone is the most potent of the androgenic hormones. Its actions on hair follicles, skin and prostate tissue is not direct however; These tissues are responsive to a form of testosterone called dihydrotestosterone (DHT); testosterone is converted to DHT by the enzyme 5-alpha-reductase. Finasteride acts by inhibiting the action of 5-alpha-reductase and thus inhibiting the conversion of testosterone into DHT.

Investigators over a number of years found that 5-alpha-reductase occurs in two forms identified as Type I and Type II, and that finasteride is effective in inhibition of Type II. Type I of the enzyme predominates in sebaceous glands. Type II occurs most abundantly in hair follicles and prostate tissue. Investigators found that:

  • Men with normal to high levels of Type II of the enzyme (and thus normal to high levels of DHT) are more likely to develop MPHL and benign enlargement of the prostate gland;
  • Men with low levels of Type II enzyme (and thus low levels of DHT) are less likely to develop MPHL and benign enlargement of the prostate; and thus
  • Inhibition of Type II 5-alpha-reductase could lower levels of DHT in hair follicles and prostate tissue and decrease the likelihood for development of MPHL and benign prostate enlargement.

Finasteride-an agent that inhibits the activity of Type II alpha-reductase and thus lowers the level of DHT in target cells-was first developed more than a decade ago to treat benign prostate enlargement. Prescribed under the brand name PROSCAR®), at a dose of 5 milligrams a day it is used in treatment of benign prostate enlargement in men.

Following the lead of finasteride’s effectiveness in treating benign prostate enlargement, investigators studied its use in treating MPHL. These studies confirmed that at a dose of 1 milligram per day, finasteride (brand name Propecia®) is effective in treating MPHL in some but not all men.

Questions about the potential for Propecia® to be associated with development or progression of prostate cancer have been addressed in a study reported in 2003. See Finasteride and Prostate Cancer for more information.

Finasteride for treatment of hair loss should be prescribed only after examination by a physician hair restoration specialist.

Finasteride is not approved the use in women, and particularly in women who are pregnant or who become pregnant. The drug has potential for interfering with sexual development of a fetus.

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