Sildenafil treats erectile dysfunction by increasing blood flow to the penis during sexual stimulation. The substance is the same under both trade names. These medicines are called PDE5 inhibitors. Oral medicine for ED also might not be safe or work well if you have: Very low blood pressure, called hypotension, or uncontrolled high blood pressure, called hypertension. United States Sildenafil is available as a generic drug in the United States, labeled for pulmonary arterial hypertension. These medicines all work well for ED.SILDENAFIL (sil DEN a fil) treats erectile dysfunction (ED). It works by increasing blood flow to the penis, which helps to maintain an erection. This medicine may be used for other . Viagra is a brand-name medication that contains the active drug sildenafil. This active drug comes as a generic medication, too. Sildenafil and brand-name Viagra . Sildenafil (Viagra). Tadalafil (Cialis). Vardenafil. These medicines are called PDE5 inhibitors. They enhance the effects of a chemical the body makes that relaxes .