Make sure you have discussed any other medications you are currently taking or plan to take before starting sildenafil with your doctor and pharmacist. Avanafil Stendra. Other uses for this medicine This medication is sometimes prescribed for other uses; ask your doctor or pharmacist for more information. It works for up to 36 hours. Your doctor will tell you not to take sildenafil if you are taking street drugs containing nitrates. The four main medicines taken by mouth for erectile dysfunction are: Avanafil Stendra. Oral medicines for ED usually work well and cause few side effects.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 . The safest way to get a prescription for Viagra is from your doctor. You can even do this over a telehealth call (on the phone or computer) in many cases, although for your first . Ask your doctor Q&A 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 .