Sildenafil should not be used with any other medicine or device that causes erections. This can happen if you are sick with fever, diarrhea, or vomiting; sweat a lot; or do not drink enough liquids. If you experience chest pain, dizziness, or nausea during sexual activity, call your doctor immediately and avoid sexual activity until your doctor tells you otherwise. Children 1 year of age and older weighing 45 kilograms kg or more—20 mg 3 times a day. For treatment of erectile dysfunction: For oral dosage form tablets : Adults up to 65 years of age—50 milligrams mg as a single dose no more than once a day, 1 hour before sexual intercourse. There is a problem with information submitted for this request.RESOURCES GETTING STARTED WITH VIAGRA Your doctor has determined that VIAGRA may be right for you. Follow his or her instructions carefully to help you get the best results from treatment. VIAGRA is available by prescription only in 25 mg, 50 mg, and mg tablets. Not actual size. TIPS FOR TAKING VIAGRA. You can take it 30 minutes to 4 hours before sexual activity. And you shouldn’t take more than one dose per day. After you try the mg dose, you can let your doctor know how your body responded. 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 adult males* with.