Do not take a double dose to make up for a missed one. Tell your doctor or pharmacist if you are taking nitrates medications for chest pain such as isosorbide dinitrate Isordil , isosorbide mononitrate Monoket , and nitroglycerin Nitromist, Nitro-Dur, Nitrostat. Patients should always ask their doctors for medical advice about adverse events. You should only be treated with one of these products at a time. Do not start these medications while taking sildenafil without discussing it with your healthcare provider.Why is this medication prescribed? Sildenafil (Viagra) is used to treat erectile dysfunction (impotence; inability to get or keep an erection) in men. According to price-comparison site , generic Revatio will cost you as little as $ per pill, depending on where you fill your prescription. That’s . Drug Images What is Viagra? If you have erectile dysfunction (ED), your doctor may recommend that you take Viagra. It’s a prescription drug that’s used in .