Finasteride is a oral inhibitör that competitively inhibits the 5-alpha-reductase type 2 enzyme, and thereby inhibits conversion of testosterone to DHT. The drug has no affinity for the androgen receptor and does not interfere with testosterone action.
Oral finasteride (1 mg daily) is FDA approved oral medication which is effective in the treatment of balding in men. It halts hair loss in 90% of patients, and partial hair regrowth occurs in 65% of those receiving finasteride. For greater efficacy, the combination of oral finasteride (1 mg once daily) and topical minoxidil can be considered.
For the treatment of male androgenetic alopecia, the recommended dose of finasteride is 1 mg per day. The medication may be taken with or without food.
Possible finasteride side effects include reversible loss of libido, reduced volume of ejaculate fluid, and erectile dysfunction, which occurs in ~2% of men. There are reports of long-lasting sexual dysfunction (post-finasteride syndrome), but its incidence is unknown. Further reported rare side effects of finasteride are alteration of mood/depression ; gynecomastia; testicular pain; hypersensitivity reactions.
Patients under treatment with finasteride should be aware of reduction of prostate-specific antigen, which is important in prostate cancer screening in men.