If you experience chest pain, dizziness, or nausea during sexual activity, call your doctor immediately and avoid sexual activity until your doctor tells you otherwise. Sildenafil Viagra is used to treat erectile dysfunction impotence; inability to get or keep an erection in men. John’s wort. If you have certain health conditions or are taking certain medications, your doctor may tell you to take sildenafil less often. Patients should always ask their doctors for medical advice about adverse events.1. Avoid taking Viagra with a large meal or high-fat meal. Viagra blood levels peak an hour after you swallow the tablet on an empty stomach. According to Ramin, if you eat a large or high-fat. Brand Names: Revatio Sildenafil is used to treat male sexual function problems (impotence or erectile dysfunction-ED). Learn more about Viagra oral. 1 This is a generic drug. Even if this drug. Brand names for sildenafil include Viagra, Revatio, and Liqrev. The cost for sildenafil oral tablet mg is around $10 for a supply of 2 tablets, depending on the pharmacy you visit. Quoted prices are for cash-paying customers and are not valid with insurance plans.