While each PDE5 inhibitor differs slightly, they’re very similar in treating erectile dysfunction. It continues to work for up to 4 hours, although its action is usually less after 2 hours. If you are taking sildenafil to treat PAH, you will probably take sildenafil three times a day with or without food. Brand names Why is this medication prescribed? If you ever need emergency medical treatment for a heart problem, the healthcare providers who treat you will need to know when you last took sildenafil. Be sure to let your doctor and pharmacist know that you are taking these medications before you start taking sildenafil. These PDE5 inhibitors may cause headache, flushing, drop in blood pressure, or other adverse effects. · 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. These medicines prevent an enzyme called phosphodiesterase type-5 from working too quickly. The penis is one of the areas where . How much does sildenafil citrate or viagra cost near you? Find the best sildenafil citrate or viagra prices near you now with our cost comparison tool and start saving today. 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 .