Finasteride is a synthetic inhibitor of the enzyme 5-alpha-reductase that converts testosterone into dihydrotestosterone. By lowering dihydrotestosterone levels in the prostate and scalp, it reduces the size of the enlarged prostate in benign prostatic hyperplasia. The drug is also prescribed for male pattern hair loss because it blocks the hormone that causes hair follicle shrinkage. This hormonal suppression allows the hair cycle to return to a more normal growth phase. The active ingredient binds selectively to the type ii isozyme of 5-alpha-reductase, producing competitive inhibition of the reaction. Inhibition limits the formation of dihydrotestosterone and thereby decreases its concentration in target tissues. As a result, both prostate tissue volume and hair follicle miniaturization are attenuated, producing the therapeutic effects observed clinically.

Finasteride is an oral medication used to treat male pattern hair loss and benign prostatic hyperplasia. It belongs to a class of drugs known as 5-alpha reductase inhibitors. The drug acts by blocking the enzyme 5-alpha reductase that converts testosterone into dihydrotestosterone. This conversion produces the androgen most responsible for prostate enlargement and scalp follicle miniaturization. Inhibition of this pathway lowers dihydrotestosterone levels, causing gradual shrinkage of an enlarged prostate and slowing hair follicle regression. The resulting reduction in androgenic stimulation improves urinary symptoms in benign prostatic hyperplasia and promotes regrowth of thicker hair on the scalp. These effects are achieved through specific interaction with androgen-responsive tissues, resulting in measurable clinical outcomes over long-term therapy.

Finasteride is a prescription medication used primarily to treat male pattern hair loss and benign prostatic hyperplasia. Some users report a decrease in sexual desire or function as a common side effect. Erectile dysfunction, including difficulty achieving or maintaining an erection, has been reported in a minority of cases. Breast tissue may become tender or enlarge in some individuals, a condition known as gynecomastia. Mood changes such as depression or anxiety have occasionally been observed in patients taking the drug. Rarely, allergic reactions like rash or swelling can occur, requiring immediate discontinuation. The medication can influence blood levels of prostate-specific antigen, which may affect diagnostic testing. Long-term safety data indicates that most side effects are reversible after stopping treatment, though individual experiences may vary.

Finasteride can reduce the levels of prostate-specific antigen in the blood. Some users experience decreased libido or erectile dysfunction. Mood changes such as depression or anxiety have been reported in a minority of patients. Breast tissue may develop tenderness or enlargement in rare cases. The drug may cause a small increase in the risk of high-grade prostate cancer. Rare allergic reactions can include rash or swelling of the face and throat. Long-term use may lead to persistent sexual side effects in some individuals.