Dutasteride (Avodart)

Dutasteride (brand name Avodart) belongs to a class of drugs called 5-alpha-reductase inhibitors, which block the action of the 5-alpha-reductase enzymes that convert testosterone into dihydrotestosterone (DHT).

Dutasteride inhibits both isoforms of 5-alpha reductase, Type I and Type II, whereas finasteride only inhibits Type II. There are no long-term randomized trials comparing the effects of dutasteride and finasteride in patients with BPH.

While dutasteride is only officially approved to treat enlargement of the prostate gland (at a dose of 0.5 mg/day), phase I and II clinical trials for dutasteride as a hair loss drug were also undertaken, but called off in late 2002. The reason the trials were called off is not publicly known. Industry sources speculate that Avodart would have been seen as too similar to Propecia (1 mg/day finasteride) to have proven itself profitable on the market as a hair loss treatment. However, phase II results indicated that dutasteride at both 0.5 mg and 2.5 mg/day generated a superior hair count to finasteride 5 mg at 12 and 24 weeks.

The off-label use of dutasteride and finasteride to reduce the risk of prostate cancer is still experimental and controversial. Although preliminary research has shown some potential findings for the medical use of dutasteride and finasteride in reducing the risk of developing prostate cancer, other research has found evidence suggesting dutasteride and finasteride only temporarily reduce the growth and prevalence of benign prostate tumors, and not only have no impact on the risk of developing prostate cancer, but also mask the detection of prostate cancer in the emergent and early low-grade stage, thus increasing the risk of a late, less treatable diagnosis and high-grade prostate cancer. The REDUCE trial, a randomized controlled trial of 6,729 men comparing dutasteride to placebo for prevention of prostate cancer, found an overall reduction of 22% in the incidence of prostate cancer over 4 years, however, the reduction was entirely in Gleason grades 5 and 6 cancers, which are less life-threatening and are often not treated. In Gleason grade 7-10, which are life-threatening, there were no reductions in cancer.