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Hundreds of dietary supplements available for sale in America between 2007 and 2016 contained "active pharmaceuticals" - drugs - that can have serious adverse affects, according to a review of data from the US Food and Drug Administration (FDA).The tainted supplements "have the potential to cause serious adverse health effects," wrote the authors, led by Jenna Tucker, a research scientist with the California Department of Food and Agriculture.Some supplements included the chemical compounds in prescription erectile dysfunction meds such Viagra or Cialis, while others contained unapproved anti-depressants, ephedrine - a stimulant banned in weight-loss pills - and "undeclared anabolic steroids or steroid-like substances".Dietary supplements are classified as food in the US and are not subject to the same rigorous testing protocols applied to drugs. They are available over the counter, and more than half of Americans use them, according to the study.The authors looked at results from the FDA's "tainted supplements" database, in which the agency publishes recall notices and consumer warnings. They note that the agency does not reveal how many products it tests each year, so the rate of adulterated supplements is unknown. A 2015 study cited in the review found that 23,000 US emergency room visits each year are due to dietary supplements.In 2010, the FDA issued a letter indicating that it had received "numerous reports of serious adverse events associated with consumer use of these tainted products including strokes, acute liver injury, kidney failure, pulmonary embolisms (artery blockage in the lung), and death".For instance, 2 to 3% of men aged 40 to 64 in the US suffer from angina - chest pain that often indicates heart disease and can be a precursor to a heart attack. The condition is commonly treated with nitrates, which can interact with sildenafil, the active ingredient in Viagra. Sildenafil or an analogue was found in 287 of 353 of the tainted sexual enhancement supplements revealed by the FDA.Pfizer's Viagra website warns of "serious side effects" and urges patients to consult a doctor before using the medication. Consumers of dietary supplements do not receive such counselling.The FDA found dapoxetine, a selective serotonin reuptake inhibitor (SSRI) that has repeatedly been denied approval in the US, in 4%, or 14, of 353 adulterated sexual enhancement supplements.It's likely that most consumers will miss FDA warnings about tainted supplements, which are not widely reported. Tucker and colleagues note that in only 44% of cases was a public notification issued. In 46%, a voluntary recall was issued, but for people who have already purchased a dietary supplement, that, too, is likely to go unnoticed.The FDA's 2010 letter notes that including banned or regulated pharmaceutical ingredients in over-the-counter products is illegal. Despite this, Tucker's team found that the FDA wrote warning letters directly to supplement manufacturers only seven times between 2007 and 2016."The presence of pharmaceutically active ingredients in dietary supplements makes them unapproved drugs and represents an important public health concern," the authors conclude.