What special precautions should I follow? Take sildenafil at around the same times every day. Also tell your doctor if you or any of your family members have or have ever had an eye disease such as retinitis pigmentosa an inherited eye condition that causes loss of vision or if you have ever had sudden severe vision loss, especially if you were told that the vision loss was caused by a blockage of blood flow to the nerves that help you see. Tell your doctor if sildenafil is not working well or if you are experiencing side effects. Without physical action to the penis, such as that occurring during sexual intercourse, sildenafil will not work to cause an erection. Sildenafil treats erectile dysfunction by increasing blood flow to the penis during sexual stimulation. Sexual activity may be a strain on your heart, especially if you have heart disease.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 . Availability. Available. See GoodRx coupons. warning. Are you looking for information on sildenafil (Revatio) instead? What is Sildenafil (Viagra)? Drug Facts. . 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 .