If you often forget doses, it may help to set an alarm to remind you. Ask your healthcare professional how you should dispose of any medicine you do not use. You may opt-out of email communications at any time by clicking on the unsubscribe link in the e-mail. If too much is used, the chance of side effects is increased. The usual dose is 50mg, when you need it. Do not take it more than once a day.Strengths: 25 mg, 50 mg, mg; Brand: Viagra. 50 mg, mg; Adult dosage (ages 18–64 years) Typical dosage: 50 mg, taken as needed about 1 hour before sexual . The dose can be increased to mg or decreased to 25mg depending on its effect. Take sildenafil up to 4 hours before you want to have sex. For sildenafil to work properly, you’ll . You may take it up to 4 hours before sexual activity. Do not take Viagra more than once per day. Shake the oral suspension (liquid) before you measure a dose. Use the dosing .