Click here for an email preview. If you are taking sildenafil to treat PAH, you will probably take sildenafil three times a day with or without food. If you are taking sildenafil to treat erectile dysfunction, you should know that it does not cure erectile dysfunction or increase sexual desire. Shake the liquid well for 10 seconds before each use to mix the medication evenly. Prolonged erections can be dangerous.Same Day Delivery. Shipping. Extenze. Original Formula Male Sexual Enhancement Tablets – 15 ea. $$ Extra 15% off $30 Sitewid Not sold at your store. Check other stores.  · 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 . VIAGRA can cause your blood pressure to drop suddenly to an unsafe level if taken with certain other medicines. Do not take VIAGRA if you take any other medicines called “nitrates.” Nitrates are used to treat chest pain (angina). A sudden drop in blood pressure can cause you to feel dizzy, faint, or have a heart attack or stroke.