Efficacy Results in Subpopulations in Controlled Clinical Studies A review of population subgroups demonstrated efficacy regardless of baseline severity, etiology, race and age. The patient addressed both questions at the final visit for the last 4 weeks of the study. Concomitant administration of strong CYP3A4 inducers, such as rifampin, is expected to cause greater decreases in plasma levels of sildenafil. Erectile dysfunction is a condition where the penis does not harden and expand when a man is sexually excited, or when he cannot keep an erection. Talk to your doctor about eating grapefruit and drinking grapefruit juice while taking this medicine.Search by NDC Enter medication name (Ex. “Lipitor”) Unsure what pill you have? Identify your drug based on shape, color or imprint. ID your medication Need drug interactions . Brand names for sildenafil include Viagra, The cost for sildenafil oral tablet mg is around $10 for a supply of 2 tablets, depending on the pharmacy you visit. Note: This is a drug discount program, not an insurance plan. Valid at all major chains including Walgreens, CVS Pharmacy, Target, WalMart Pharmacy, Duane Reade and 65, Rarely reported side effects include: an erection that will not go away (priapism). If you have an erection that lasts more than 4 hours, get medical help right away. If it is not treated right away, priapism can permanently damage your penis. sudden vision loss in one or both eyes.