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 .If you are taking sildenafil to treat erectile dysfunction, follow your doctor’s directions and the guidelines in this paragraph. If you experience chest pain, dizziness, or nausea during sex, seek immediate medical help. Brand names Why is this medication prescribed? If you have an erection that lasts more than 4 hours, get medical help right away. What should I do if I forget a dose?Sildenafil (Viagra) is used to treat erectile dysfunction (impotence; inability to get or keep an erection) in men. Sildenafil (Liqrev, Revatio) is used to improve the ability to exercise in . 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 . The Savings Offer and Program expire on 12/31/ For further information, call , visit , or write: Viatris Inc., P.O. Box , Mission, KS .What side effects can this medication cause? What should I do if I forget a dose? Continue to take sildenafil even if you feel well. If you are taking sildenafil for PAH, take the missed dose as soon as you remember it. Tell your doctor if any of these symptoms are severe or do not go away: headache.