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 .Children 1 year of age and older weighing 20 to 45 kg—20 mg 3 times a day. Do not press on the plunger of the syringe. Remove the cap by pushing it down and twisting it counter-clockwise. Dosing The dose of this medicine will be different for different patients. How to take liquid If you or your child are taking sildenafil as a liquid, 1ml is usually the same as taking a 10mg tablet, but it’s important to always check the medicine label.Overdose 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 . Last updated on Uses Warnings Before taking Dosage Side effects Interactions FAQ What is Viagra? Viagra relaxes muscles found in the walls of blood . Viagra is approved for this use in males ages 18 years and older. Viagra contains the drug sildenafil. It belongs to a class of drugs called phosphodiesterase type 5 (PDE5) .Leading causes of ED are listed below. Erectile dysfunction symptoms include persistent: Trouble getting an erection Trouble keeping an erection Reduced sexual desire Men of any age may benefit from the use of Viagra Sildenafil if they experience any of the above symptoms. Take sildenafil up to 4 hours before you want to have sex. This medicine comes with a patient information leaflet. Do not use a kitchen teaspoon as it will not measure the right amount. Men as young as 18 may experience ED. If you are a Mayo Clinic patient, this could include protected health information.