Sildenafil treats erectile dysfunction by increasing blood flow to the penis during sexual stimulation. It might work longer if you have mild to moderate erectile dysfunction. Do not stop taking sildenafil without talking to your doctor. Tell your doctor if any of these symptoms are severe or do not go away: headache. Take sildenafil as needed before sexual activity. These are commonly prescribed for an enlarged prostate or male pattern baldness.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 . Sildenafil (Viagra). Tadalafil (Cialis). Vardenafil. These medicines are called PDE5 inhibitors. They enhance the effects of a chemical the body makes that relaxes muscles . Viagra is used as needed, meaning you only take a dose prior to sexual activity. Cialis can be prescribed for use as needed, but can also be prescribed for use once per day, every .