Sildenafil (Viagra) is used to treat erectile dysfunction (impotence; inability to get or keep an erection) in men. Sildenafil (Revatio) is used to improve the ability to exercise in adults with pulmonary arterial hypertension (PAH; high blood pressure in the vessels carrying blood to the lungs, causing shortness of breath, dizziness, and tiredness). Children should not usually take sildenafil, but in some cases, a doctor may decide that sildenafil (Revatio) is the best medication to treat a child’s condition. Sildenafil is in a class of medications called phosphodiesterase (PDE) inhibitors. Sildenafil treats erectile dysfunction by increasing blood flow to the penis during sexual stimulation. This increased blood flow can cause an erection. Sildenafil treats PAH by relaxing the blood vessels in the lungs to allow blood to flow easily.

If you are taking sildenafil to treat erectile dysfunction, you should know that it does not cure erectile dysfunction or increase sexual desire. Sildenafil does not prevent pregnancy or the spread of sexually transmitted diseases such as human immunodeficiency virus (HIV).

Sildenafil may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

• headache
• heartburn
• diarrhea
• flushing (feeling of warmth)
• nosebleeds
• difficulty falling asleep or staying asleep
• numbness, burning or tingling in the arms, hands, feet, or legs
• muscle aches
• changes in color vision (seeing a blue tinge on objects or having difficulty telling the difference between blue and green)
• sensitivity to light

Some side effects can be serious. If you experience any of the following symptoms, call your doctor immediately:

• sudden severe loss of vision (see below for more information)
• blurred vision
• sudden decrease or loss of hearing
• ringing in ears
• dizziness or lightheadedness
• fainting
• chest pain
• worsening shortness of breath
• erection that is painful or lasts longer than 4 hours
• itching or burning during urination
• rash