The FDA says laboratory analysis confirmed that the product, Wonder-Erect Male Gum, contains vardenafil but doesn't say so on the label.

Vardenafil is the active ingredient in the prescription drug Levitra, which is FDA approved for treating erectile dysfunction. However, it can lead to dangerous side effects when combined with nitrates, which many men take to treat diabetes, high blood pressure, high cholesterol, or heart disease. Nitrates are also included in some street drugs. The combination of vardenafil and nitrates can cause blood pressure to plummet to dangerous levels.

The gum is sold on various websites, including Amazon.com, and may also be stocked in some retail stores, the FDA said in an advisory statement posted online.

The agency urged patients and doctors to report any cases of harm from the product to the FDA.

Health officials are concerned about a growing trend involving over-the-counter products, frequently marketed as dietary supplements, containing hidden ingredients that could be harmful. The FDA says this is increasingly becoming a problem in products promoted for sexual enhancement. Dangerous diet pills sold online have also been linked to complications and even deaths in recent years.