Children—Use is not recommended. Sildenafil usually should not be taken more than once every 24 hours. Numerous sites on the Internet offer Viagra for sale after an “online consultation”, often a simple questionnaire. Retrieved 6 October Place the tip of the syringe into you or your child’s mouth and point it towards the cheek. Pfizer Canada Inc. · Generic name: sildenafil (oral) [ sil-DEN-a-fil ] Brand names: Revatio, Viagra Drug classes: Agents for pulmonary hypertension, Impotence agents Medically reviewed . Sildenafil oral tablet is used to treat erectile dysfunction (ED). It’s also used to treat pulmonary arterial hypertension (PAH). What is sildenafil? Sildenafil is a .  · 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. .