Propecia and Proscar are formulations of the drug finasteride. These medications are used to treat male pattern baldness and prostatic hypertrophy. Prior studies have found side effects including sexual changes (loss in libido and function) and now new studies are finding increased incidence of male breast cancer in some of the patients taking the drugs.
Health Canada has issued a warning:
Although the apparent risks are low, Health Canada issued a warning Thursday telling consumers the drug, finasteride, could be potentially dangerous. The drug, which comes in one-milligram and five-milligram formats, is used in the lower dose to treat baldness and the higher dose to treat non-cancerous enlarged prostate. Previous studies have raised flags about the five-milligram format, sold in Canada under the brand name Proscar, including an increased risk of prostate cancer.
As these drugs inhibit the action of the male sex hormone DHT (Dihydrotestosterone,) it is empirically reasonable to see how they might affect risks of hormone-related cancers like breast cancer and prostate cancer. These studies do not definitely establish an association however.
Having been taking finasteride for the last several years (at low doses) to inhibit my own hair loss without destroying my sex life, I am not stopping it anytime soon. Keeping the dose low however does decrease sexually associated (and undesirable) side effects. It might also decrease other risks as well if additional studies confirm these suspicions.
*This blog post was originally published at Truth in Cosmetic Surgery*