The American Food and Drug Administration (FDA) recently added a warning to the labeling of 5-alpha reductase inhibitors, a class of drugs used widely to treat benign prostatic hyperplasia (BPH - sometimes simply called "enlarged prostate") as well as hair loss. Drugs included in this group include Proscar, Propecia, and Avodart.
Proscar and Avodart have been widely used in men who are at higher risk of developing prostate cancer with the thought that their anti-androgen effects may lower the risk of developing prostate cancer. While there is some evidence that this may be the case, the drugs have never been formally approved for use in prostate cancer prevention.
The new warning comes after a study showed that men taking these medications may be at slightly higher risk of developing high grade aggressive prostate cancer. The warning does not refer to an overall increase in prostate cancer rates among men taking the drugs, but rather that the prostate cancer developed by these men were slightly more likely to be aggressive.