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. It works for up to 36 hours. They’re often the first line of treatment for trouble getting or keeping an erection, called erectile dysfunction ED. Side effects Side effects of oral ED medicines are often mild. Avanafil Stendra.VIAGRA is available by prescription only in 25 mg, 50 mg, and mg tablets. Patients should always ask their doctors for medical advice about adverse events. You are . 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 Missing: requirements.