March 4, 2015 -- Testosterone-boosting drugs taken by millions of American men have never been proven to be safe or effective for treating aging-related problems such as low sex drive and fatigue, the U.S. Food and Drug Administration says.
On Tuesday, the agency also said the drugs can increase the risk of heart attack and told manufacturers they must add that caution to the warning labels on the products, the Associated Press reported.
A similar warning about testosterone drugs was issued last summer by Canadian health officials.
The agency also told drug companies must clarify that the drugs are only approved to treat low testosterone levels caused by injury or disease.
For years, testosterone pills, patches, gels and injections have been marketed as treatments for low testosterone levels, and sales of the drugs have risen to more than $2 billion.
"There's been a very successful advertising campaign to make men feel that whatever their problem is, the answer is to buy more testosterone," Dr. Sidney Wolfe, of the consumer advocacy group Public Citizen, told the AP.
Last February, the group petitioned the FDA to have testosterone drugs carry a boxed warning -- the most serious type -- about heart risks, but the FDA said there was "insufficient evidence" for such a warning and rejected the petition.
The FDA launched a safety review of testosterone drugs in January 2014 after two federal studies linked them with higher rates of serious problems such as heart attack and stroke. However, other studies have suggested an association between testosterone replacement and longevity, the AP reported.
Men's testosterone levels naturally decrease after age 40, but there is disagreement on whether this actually causes problems such as lower bone density and less energy.