Ask your healthcare professional how you should dispose of any medicine you do not use. This medicine comes with a patient information leaflet. For treatment of erectile dysfunction: For oral dosage form tablets : Adults up to 65 years of age—50 milligrams mg as a single dose no more than once a day, 1 hour before sexual intercourse. Sildenafil comes as a tablet and suspension liquid to take by mouth. This medication is taken with or without food an hour before sex. Kidney disease that needs to be treated with dialysis. Other uses for this medicine This medication is sometimes prescribed for other uses; ask your doctor or pharmacist for more information.VIAGRA usually starts to work within minutes. You may take it up to 4 hours before sexual activity. So there’s no need to rush. Eat smart before you start. VIAGRA can be taken with or without food. If you take VIAGRA after a high-fat meal (such as a cheeseburger and french fries), it may take a little longer to start working. Drug Images What is Viagra? If you have erectile dysfunction (ED), your doctor may recommend that you take Viagra. It’s a prescription drug that’s used in adult males* with ED. With ED. Interactions. 1. How it works. Sildenafil may be used to treat erectile dysfunction (ED or impotence) in men (Viagra brand) or pulmonary arterial hypertension in both men and women (Revatio brand), depending on the brand. Sildenafil blocks the action of an enzyme known as cGMP-specific phosphodiesterase type-5 (PDE-5).