Sildenafil treats erectile dysfunction by increasing blood flow to the penis during sexual stimulation. If you will be taking this medicine for pulmonary arterial hypertension, your doctor will want to check your progress at regular visits. Do not mix the liquid with other medications or add anything to flavor the medication. Sudden vision loss in one or both eyes can be a sign of a serious eye problem called non-arteritic anterior ischemic optic neuropathy NAION. Therefore, inhibitors of these isoenzymes may reduce sildenafil clearance and inducers of these isoenzymes may increase sildenafil clearance.Examples of Viagra’s more commonly reported side effects include: headache. flushing (temporary warmth, redness, or deepening of skin color) stuffy nose. indigestion (upset stomach) mild vision. About sildenafil (Viagra) 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). If you have erection problems sildenafil works by temporarily increasing blood flow to your penis when.  · Viagra; Descriptions. Sildenafil is used to treat men who have erectile dysfunction (also called sexual impotence). Sildenafil belongs to a group of medicines called phosphodiesterase 5 (PDE5) inhibitors. Adults 65 years of age and older—25 mg as a single dose no more than once a day, 1 hour before sexual intercourse. Alternatively, the.