If you have certain health conditions or are taking certain medications, your doctor may tell you to take sildenafil less often. Be sure to let your doctor and pharmacist know that you are taking these medications before you start taking sildenafil. If you buy sildenafil for erectile dysfunction, it can also be known by the brand names Viagra, Aronix, Liberize and Nipatra. Before taking sildenafil, tell your doctor and pharmacist if you are allergic to sildenafil, any other medications, or any of the ingredients in sildenafil tablet or suspension. Do not take a double dose to make up for a missed one.In , a meta-analysis of trials determined that while Viagra is the most effective of the various ED drugs on the market, it also has the highest incidence of side effects—headache, upset stomach, vision loss, blue-tinged sight, back pain, muscle pain, nausea, and dizziness, just to name a few common ones. 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. Sildenafil (Viagra) is used to treat erectile dysfunction (impotence; inability to get or keep an erection) in men. 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 hypertension (PAH; high blood pressure in the vessels carrying blood to the .