Finasteride for the treatment of male pattern baldness

The use of Finasteride (brand name propecia), a synthetic 4-azasteroid compound, is indicated in men older than 18 years with mild to moderate male pattern hair loss. The underlying principle behind the use of this drug in male pattern hair loss is the reduction of dihydrotestosterone (DHT) production; thus limiting the action of DHT on scalp hair follicles.

The microsomal enzyme steroid 5 -reductase is responsible for the formation of potent DHT from testosterone as well as for the conversion of androstenedione to 5a-androstanedione. Finasteride in the treatment of androgenetic alopecia acts as a potent 5 -reductase inhibitor without any androgenic, antiandrogenic, or other steroid hormone activities. Finasteride has a higher affinity for the 5 alpha – Reductase – 2 (5 R-2) rather than 5 alpha – Reductase – 1 (5 R-l).

DHT Dihydrotestosterone
DHT Dihydrotestosterone – Androgen

Absorption of finasteride


Maximum plasma levels of Finasteride are achieved 1 to 2 hours after oral dosing, with a mean plasma half-life of 6 hours. Being a non-competitive antagonist, Finasteride binds irreversibly to the enzyme and inhibits the conversion of testosterone to dihydrotestosterone (DHT). Thus, while the pharmacokinetic half-life is about 8 hours, the biological effect lasts for much longer.

Metabolism of finasteride

Finasteride is extensively metabolized in the liver, primarily via the cytochrome P450 3A4 enzyme subfamily. There are no known drug interactions. Approximately 40 percent of the drug is excreted in the urine and 60 percent in the feces, most as monocarboxylic acid. Metabolites possess less than 20 percent of the 5 -Reductase inhibitory activity compared with Finasteride.

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Clinical trials in male pattern hair loss

Various studies have shown the beneficial effects of Finasteride on reversing the pathogenesis of hair loss in male androgenetic alopecia. Most of these studies show the effects of Finasteride in stimulating a substantial amount of hair re-growth, reaching its peak efficacy after 1 year of treatment, and slowing the progression of hair loss thereafter.

  • Three recent double-blind, placebo-controlled clinical trials have demonstrated that 1 mg Finasteride taken daily for at least 12 months prevented progression of hair loss and produced significantly greater increase in hair counts in comparison with placebo in men with mild to moderate hair loss. Photographic evaluation of subjects after 1 year of treatment showed clinical improvement in 48 percent as opposed to 7 percent with placebo. The percentage of subjects who showed progress with this treatment increased to 66 percent by the end of the second year.
  • A study measuring hair counts using macrophotographs found that with the treatment of Finasteride there was an increase in both total and anagen hair counts as well as an increase in the anagen to telogen ratio. This study showed that Finasteride probably has the capacity to stimulate conversion of hair follicles into the anagen phase, possibly through reversion of the decrease in anagen phase and the increase in lag phase.
  • A study of scalp biopsies found that Finasteride stimulates an increase in terminal hair counts and a decrease in vellus hair counts.
  • Findings from another study using hair count and hair weight as an objective measure of outcome demonstrated that both hair count and hair weight increases, with a larger extent of increase achieved in hair weight. This proves the ability of Finasteride to reverse the miniaturization process, producing hair of greater length and thickness, and possibly with a greater growth rate.
  • The efficacy of topical Finasteride has also been investigated as an alternative mode of administration. Although 0.05 percent of Finasteride solution applied to the scalp was well absorbed and produced a 40 percent reduction in serum DHT, it had no effect on hair re-growth. This is probably because a reduction in circulating DHT is required in addition to the local blockade of 5a-reductase at the hair follicle.
  • Studies are now under way to evaluate Finasteride 1mg in older men with androgenetic alopecia as well as those with more extensive loss.
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Efficacy of finasteride in men

Finasteride brand name propecia
Finasteride propecia

Finasteride (1 mg daily) has been approved for the treatment of male pattern hair loss in the United States as well as in several European countries. It has been found that oral Finasteride at doses of 1 and 5 mg per day causes a marked suppression of serum DHT of 71.4 and 72.2 percent, respectively and suppression in the scalp DHT of 64.1 and 69.4 percent, respectively. Treatment must be continued for at least 6 months before a proper evaluation of efficacy can be made. Although it affects vertex balding more than frontal hair loss, the medication has been shown to increase re-growth in the frontal area as well.

Finasteride is available as the brand name Propecia, which was developed to treat male pattern hair loss in the vertex and anterior mid-scalp area. Propecia is proven to maintain or increase hair count in most men.

Combined use of Finasteride and topical Minoxidil

Small-scale, variably controlled studies conducted on a primate model for androgenetic alopecia and on young men with mild to moderate male pattern hair loss showed that combination of Finasteride and Minoxidil may be more effective than any one drug alone, but further investigation is needed to sustain this theory.

Side effects in Men

Some common side effects of Finasteride treatment in men according to authors are decreased libido, decreased semen volume, and erectile dysfunction, with each occurring in fewer than 2 percent of men younger than 41 years and slightly more often in older men. Contrarily, a recent study by Overstreet et al showed that Finasteride 1mg daily for 48 weeks does not affect spermatogenesis or semen production in men aged 19 to 41 years.

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Many recipients of this drug are elderly men taking 5 mg per day. There is no effect of long-term use on bone mineral density. Reversible painful gynaecomastia (abnormal enlargement of the male mammary glands) has been reported and the incidence is thought to be around 0.001 percent. Many of these adverse effects in men on Finasteride resolved while they remained on drug itself, and any remaining adverse effects were cleared up once the drug was stopped. With regards long-term safety, Finasteride for men has now been in medical use for over 10 years.