Levitra vardenafil : This medication is taken one hour before sex and can last up to 24 hours. Most erectile dysfunction medications belong to the drug class known as PDE5 inhibitors , which help relax the muscles and increase blood flow to allow for a full erection. Generic vs. Your doctor may adjust your dose if needed. Before taking sildenafil, tell your doctor and pharmacist if you are allergic to sildenafil, any other medications, or any of the ingredients in sildenafil tablet or suspension.Breastfeeding. For professionals. Drug Images. What is Viagra? Viagra is a brand-name prescription drug that’s approved to treat erectile dysfunction (ED). With ED, you’re . Sildenafil (Viagra) is used to treat erectile dysfunction (impotence; inability to get or keep an erection) in men. Sildenafil (Liqrev, Revatio) is used to improve the ability to exercise in adults (Liqrev, Revatio) and children 1 year of age and older (Revatio) with pulmonary arterial hypertension (PAH; high blood pressure in the vessels carrying blood to the . Sildenafil is best known as a treatment for ED, the inability to get or keep an erection. Sildenafil is meant to be taken before having sex, with the understanding that its effects last only a few.