Priapism, or an erection lasting longer than four hours, is also a potential serious side effect. If you take any of the above medications, discuss your options with your doctor. It’s available in 50 mg, mg, and mg tablets. People taking nitrates like nitroglycerin Nitrostat or isosorbide mononitrate Imdur should not take PDE5 inhibitors, as doing so could result in a dangerous drop in blood pressure. You should also call your insurance company to see if they cover erectile dysfunction medications.Learn More IF YOU CHOOSE BRAND-NAME VIAGRA, MAKE SURE YOU GET THE BRAND NAME 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 prescribed and, if eligible, save on your prescription. Ask Your Doctor.  · What is sildenafil? Sildenafil relaxes muscles of the blood vessels and increases blood flow to particular areas of the body. Sildenafil under the name Viagra is used to treat erectile dysfunction (impotence) in men. According to price-comparison site test1.ru, generic Revatio will cost you as little as $ per pill, depending on where you fill your prescription. That’s compared with more than $50 per.