In the hawking of nutritional supplements that claim to enhance sexual performance, the names alone have to do a lot of the carny barking.

Take, Man Up Now, the provocative brand name for pills containing a bunch of herbs that their marketer says can enhance a man’s sexual performance. No prescription is required, and the product’s website touts marathon sexual staying power “without harmful side effects.”

But the Food and Drug Administration disagrees and is warning men to steer clear of Man Up Now.

The agency says the pills have been found to contain sulfoaildenafil, a chemical cousin of Viagra that, like the prescription medicine, could lead to sudden drops in blood pressure in men also taking nitrates, such as nitroglycerin, for heart conditions.

The company didn’t immediately respond to a request for comment sent to its website.

In the warning about Man Up Now, the FDA reminds consumers that just because a product claims to be “herbal” or “all natural” doesn’t mean it’s free of risks.

Previously the agency found about a third of supplements claiming to enhance sexual performance contained undeclared prescription drug ingredients, such as sildenafil (aka Viagra), or close chemical variants. Copyright 2010 National Public Radio.