Chinese-made 'dietary supplements' may contain active ingredient found in Viagra according to the US drug safety watchdog. They warned on their website that this could be harmful to consumers.
"The US Food and Drug Administration (FDA) is advising consumers not to buy or use Super Shangai, Strong Testis, Shangai Ultra, Shangai Ultra X, Lady Shangai, and Shangai Regular, also marketed as Shangai Chaojimengnan, products," the FDA said in a statement.
"These products, which originate in China, are being marketed for the treatment of erectile dysfunction and for sexual enhancement," the statement said.
None of the product labels mention that they contain sildenafil, the active drug in Viagra, or a similar compound, it said.
"The undeclared ingredients in these products may interact with nitrates found in some prescription drugs and can lower blood pressure to dangerous levels," the statement warned.
Particularly at risk are sufferers of diabetes, high blood pressure, high cholesterol, or heart disease.
"Erectile dysfunction is a common problem in men with these medical conditions," the FDA statement said.
"Because they may have been advised against taking erectile dysfunction drugs, they may seek out products like these because they are marketed as 'all natural' or as not containing the active ingredients in approved drugs."
The products, which were distributed in the United States by a company based in Puerto Rico, have not been approved by the FDA and are illegal.