According to the FDA...

"FDA laboratory analysis confirmed that La Pepa Negra contains sildenafil, the active ingredient in the FDA approved prescription drug Viagra, used to treat erectile dysfunction (ED). This undeclared ingredient 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."

http://www.fda.gov/Drugs/ResourcesForYou/Consumers/BuyingUsingMedicineSafely/MedicationHealthFraud/ucm436426.htm