However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Sexual activity may be a strain on your heart, especially if you have heart disease. Before taking sildenafil, tell your doctor and pharmacist if you are allergic to sildenafil, any other medications, or any of the ingredients in sildenafil tablet or suspension. From Mayo Clinic to your inbox Sign up for free and stay up to date on research advancements, health tips, current health topics, and expertise on managing health. The following nonprescription or herbal products may interact with sildenafil: cimetidine Tagamet HB , St. What special dietary instructions should I follow? Sildenafil is also used in both men and women to treat the symptoms of pulmonary arterial hypertension.What is sildenafil? Sildenafil relaxes muscles of the blood vessels and increases blood flow to particular areas of the body. Sildenafil under the name Viagra is used to treat erectile . 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 . Viagra is available in three strengths: 25 milligrams (mg), 50 mg, and mg. Note: Sex and gender exist on spectrums. Use of the term “male” in this article refers to sex .