Nitrates are prescription medicines used for treatment of angina such as nitroglycerin, isosorbide mononitrate, or isosorbide dinitrate. It should be kept out of sight and reach of children. Before you start taking Viagra, be sure to tell your doctor if you: Have a heart disease such as irregular heartbeats, angina, chest pain or had a heart attack in the past. This medicine is used in the treatment of high blood pressure in blood vessels between the heart and the lungs. A serious drop in blood pressure can lead to dizziness, fainting, and rarely heart attack or stroke. Practice “safe sex” such as using latex condoms.Brand Name Viagra Common Name sildenafil In this drug factsheet: How does this . Instructions Certain heart medication (nitrates) must be avoided while taking this product. . Be aware that a medication that does not need a prescription in another country could .