This medicine is available only with your doctor’s prescription. They enhance the effects of a chemical the body makes that relaxes muscles in the penis, called nitric oxide. Be sure to let your doctor and pharmacist know that you are taking these medications before you start taking sildenafil. The products discussed in this site may have different product labeling in different countries. When oral medications might not be safe Check with your health care team before you take any medicine for erectile dysfunction. · Sildenafil is used to treat men who have erectile dysfunction (also called sexual impotence). Sildenafil belongs to a group of medicines called phosphodiesterase . Sildenafil (Viagra). This medicine works best when you take it on an empty stomach an hour before sex. The body takes longer to absorb it after a high-fat meal or . CHOOSE BRAND-NAME VIAGRA. The original little blue pill prescribed by doctors for over 20 years. Clinically proven to treat men with erectile dysfunction (ED) Ongoing .