Do you drink alcohol? Sildenafil treats erectile dysfunction by increasing blood flow to the penis during sexual stimulation. If you become pregnant while taking sildenafil, call your doctor. If too much is used, the chance of side effects is increased. Children 1 year of age and older weighing 20 to 45 kg—20 mg 3 times a day.Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take sildenafil exactly as directed. . It can be treated: Sometimes, it’s as simple as taking a pill your doctor prescribes. There are drugs just for ED. Other options your doctor can help you explore include: Injections;. 1. How it works Sildenafil may be used to treat erectile dysfunction (ED or impotence) in men (Viagra brand) or pulmonary arterial hypertension in both men and women (Revatio .