Brand names Why is this medication prescribed? Keep from freezing. Place the tip of the syringe into you or your child’s mouth and point it towards the cheek. New Zealand Sildenafil was reclassified in New Zealand in so it could be bought over the counter from a pharmacist. Dosing The dose of this medicine will be different for different patients. Remove the cap by pushing it down and twisting it counter-clockwise. The following information includes only the average doses of this medicine. · 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. .