Do not take more or less of it or take it more often than prescribed by your doctor. You should only be treated with one of these products at a time. Also tell your doctor if you or any of your family members have or have ever had an eye disease such as retinitis pigmentosa an inherited eye condition that causes loss of vision or if you have ever had sudden severe vision loss, especially if you were told that the vision loss was caused by a blockage of blood flow to the nerves that help you see. 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. Rarely reported side effects include: an erection that will not go away priapism. Severe liver disease.Your prescription may have been filled with a generic version instead of brand-name VIAGRA. Follow the steps below to help ensure you receive the brand name your doctor . According to price-comparison site , generic Revatio will cost you as little as $ per pill, depending on where you fill your prescription. That’s compared with . 1. How it works Sildenafil may be used to treat erectile dysfunction (ED or impotence) in men (Viagra brand) or pulmonary arterial hypertension in both men and women (Revatio .