Vardenafil usually works for 4 to 5 hours. Your doctor may need to change the doses of your medications or monitor you carefully for side effects. You should only be treated with one of these products at a time. Avanafil Stendra. When choosing one, tell your doctor or other health care professional what your preferences are, such as cost, ease of use, how long the drug’s effects last and side effects. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand.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 . Viagra is a brand-name medication. It’s also available in a generic form called sildenafil. How does Viagra work and how long does it last? You may have . Oral medicines for ED usually work well and cause few side effects. The four main medicines taken by mouth for erectile dysfunction are: Avanafil (Stendra). Sildenafil .