Finasteride, brand-name Propecia or Proscar among others, is a synthetic anti-androgen that acts primarily through the inhibition of the 5-AR (5-alpha-reductase) enzyme, which is primarily responsible for converting testosterone into DHT (di-hydro-testosterone). 5-AR reduces the 4,5 double bond of testosterone which converts it into the biologically-active DHT hormone, which is three times more potent than testosterone; production of DHT via conversion from testosterone takes place primarily in the hair follicles, prostate, testicles, and adrenal glands. DHT is not converted to estradiol via aromatase.
DHT is the primary factor implemented in common male pattern baldness and occasionally is the primary factor in female hair loss. DHT plays a role in the development and progression of benign prostatic hyperplasia (BPH), as well as in prostate cancer, via enlargement of the prostate gland. Normal growth of prostate cells and prostate cell differentiation also depends heavily on DHT.
Finasteride is applied in BPH treatment at a dose of 5 mg taken once daily. Typical treatment is effective within six months, with reversal of therapeutic benefits typical if treatment with finasteride is ceased. Finasteride also treats the symptoms associated with BPH: difficulty urinating ("prostate pinch"), sleep disturbance at night due to excessive frequency of urination, difficulty initiating urination, and decreased urinary flow.
In different, 5-year long, study of men experiencing mild to moderate hair loss, 48% of those treated with Propecia (1 mg of finasteride) had some regrowth of hair, and a further 42% had no further loss. Hair count in the treatment group remained above baseline on average, with increasing difference from hair count in the placebo group, for the duration of the study. Finasteride is effective only for as long as it is taken; the hair gained or maintained is lost within 6–12 months of ceasing therapy. Finasteride, like minoxidil (Rogaine), was shown to work on both the crown area and the hairline with significantly more success in reversing hair-loss in the crown region.
The 2005 Prostate Cancer Prevention Trial (PCPT) demonstrated, with dosage of 5 mg per day as is indicated normally for BPH, study subjects taking finasteride were 25% less likely to have developed prostate cancer at the end of the trial when compared to those taking a placebo. It initially appeared (though was later shown to be incorrect) as though finasteride increased the specificity and selectivity of prostate cancer detection, with an apparent result of increasing rates of Gleason grade tumors, but 2008 update of this study found that finasteride reduces the incidence of prostate cancer by 30%. The smaller prostate caused by finasteride means that a clinician is more likely to detect aggressive-looking cells within a cancerous area. The second study concluded that finasteride did not increase the risk of high-grade prostate cancer.
MERCK Corp Patient Information About Proscar (PDF):
MERCK Consumer Information: Finasteride Clinical Study Accessed 05-20-2010.
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*The latter article is intended for educational / informational purposes only. THIS PRODUCT IS INTENDED AS A RESEARCH CHEMICAL ONLY. This designation allows the use of research chemicals strictly for in vitro testing and laboratory experimentation only. Bodily introduction of any kind into humans or animals is strictly forbidden by law.