Do not take a double dose to make up for a missed one. If you take too much sildenafil or take it together with these medicines, the chance for side effects will be higher. It affects the way the medicine works. Alternatively, the medicine may be taken 30 minutes to 4 hours before sexual intercourse. The information provided is for educational purposes only and is not intended to replace discussions with a healthcare provider. 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.AdDon’t go to the pharmacy without checking prices at GoodRx® first. No commitment or fees. Find the lowest price in your neighborhood & use our free coupons to save up to 80%Service Catalog: Erectile Dysfunction, Levitra, Cialis, Side Effects and more. Erectile dysfunction is when a man has difficulty getting an erection or keeping it long enough for sex. It’s also known as ED or impotence. It happens when not enough blood flows to the penis, preventing an erection. The frequency increases with age, affecting about 50% of men over age 40*; however younger men may also experience ED.  · 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 .