All of the drugs must change their labels to warn of the risk, which unexpectedly appeared in two different large-scale clinical trials.
Ironically, Proscar and Avodart appear to reduce the risk of low-grade prostate cancer, which is less aggressive than high-grade prostate cancer. But the increased risk of high-grade prostate cancer means the drugs can't claim to lower overall prostate cancer risk.
The FDA ruling follows the December 2010 vote of an FDA advisory panel, which rejected requests from Merck (for Proscar) and GlaxoSmithKline (for Avodart) to claim that the drugs prevent prostate cancer.
The male hair-loss drug Propecia has the same active ingredient as Proscar, although at one-fifth the dose. But the FDA says Propecia should carry the same prostate cancer warning as Proscar.
Even though the drugs are linked to prostate cancer, the risk is small. Men who are taking Proscar, Avodart, or Jalyn for benign prostatic hyperplasia (BPH) should not stop taking their medications, but should consult their doctors about their prostate cancer risk.
Proscar, Avodart, and Propecia are in the same class of drugs, known as 5-alpha-reductase inhibitors or 5-ARIs. Jalyn has the same active ingredient as Avodart, together with a drug called tamsulosin (Flomax). The FDA warning does not include Flomax, which is in a different class of prostate drugs called alpha blockers.
Other alpha blockers include Cardura, Hytrin, Uroxatral, and Rapaflo. Unlike the 5-ARI drugs, the alpha blockers are effective in treating the symptoms of BPH but have not been shown to reduce the risk of urinary retention due to an enlarged prostate.