The Food and Drug Administration is warning consumers to stay away from “Sex Drive Capsules,” a product promoted for sexual enhancement.

The warning was issued after the investigators found the product contains sildenafil, the active ingredient in the prescription drug Viagra, which is used to treat erectile dysfunction.

Sildenafil may interact with nitrates found in some prescription drugs such as nitroglycerin and may lower blood pressure to dangerous levels.  Men with diabetes, high blood pressure, high cholesterol, or heart disease often take nitrates, the regulators say.

The undeclared ingredient was found during an investigation of international mail shipments prompted by the agency's concern over  the growing trend of dietary supplements or conventional foods manufactured with hidden drugs and chemicals.

The FDA advises that people use caution when purchasing products that are typically promoted for sexual enhancement, weight loss, and body building and are often represented as being “all natural.”