[Therapy of androgenetic alopecia with finasteride. What must be considered in consultation and drug prescribing].

Androgenetic alopecia in men is genetically determined, but occurs only when the testosterone metabolite dihydrotestosterone (DHT) is present in normal levels. The drug, finasteride, inhibits the enzyme 5-alpha-reductase II, which is responsible for converting testosterone to DHT. One 1 mg tablet (Propecia) of finasteride daily lowers serum DHT levels by about 70%, and increases serum testosterone by 10%. The efficacy of finasteride 1 mg has been demonstrated in a randomized, double-blind, placebo-controlled clinical trial involving more than 1,500 men in whom a significant increase in hair density over a specified area of the scalp, and a significant improvement in appearance was noted. Following one year to treatment 48%, and following 2 years 66%, of the finasteride patients (placebo group 7% after both treatment periods) presented with visibly thicker hair growth. Side effects such as decreased libido, ejaculation disorders and erectile dysfunction were seen in fewer than 2% of the men in both the finasteride and placebo groups.