Sildenafil is a medicine used to treat erection problems (erectile dysfunction). Sildenafil is also sometimes used to treat pulmonary hypertension (high blood pressure in the blood vessels that supply the lungs). Sildenafil is an effective oral treatment for ED that produces a penetrative erection as early as 12 min and for most patients, within 30 min after dosing, and a duration of action lasting at least 4 hours