The patients in studies had varying degrees of ED. Rarely reported side effects include: an erection that will not go away priapism. Children 1 year of age and older weighing 45 kilograms kg or more—20 mg 3 times a day. The primary endpoint was time to limiting angina in the evaluable cohort. Your doctor may adjust your dose as needed and tolerated.The recommended dosage of Viagra for erectile dysfunction (ED) is 50 mg, taken as needed about 1 hour before sexual activity. You can take it 30 minutes to 4 hours before sexual activity. And you. 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. Alternatively, the . Viagra can help you have an erection when sexual stimulation occurs. An erection will not occur just by taking a pill. Follow your doctor’s instructions. During sexual activity, if you .