These include a heart attack, stroke or a serious heart rhythm disorder in the past six months. What Are the Symptoms of Erectile Dysfunction? This is important for your overall health and safety, as certain medications can negatively interact with each other or cause existing conditions to worsen. These medicines are called PDE5 inhibitors. A phone or video consultation is sometimes required for legal purposes. This increase in blood flow results in a firmer, longer-lasting erection.Sildenafil (Viagra, Revatio) is a moderately priced drug used to treat erection problems in men. It is also used to treat pulmonary arterial hypertension, a serious heart and lung . Typical dosing for Sildenafil (Viagra) The typical dose is to take 50 mg of sildenafil (Viagra) by mouth, about 1 hour before sex, as needed. The maximum recommended dose is . Generic Viagra usually costs anywhere from about $2–$18 for each tablet depending on the dosage and manufacturer. Can I buy generic Viagra without a prescription? No.