Ask your pharmacist for a list of the ingredients. Some medications should not be taken with sildenafil. Take sildenafil at around the same times every day. What side effects can this medication cause? Tell your doctor if any of these symptoms are severe or do not go away: headache.Sildenafil (Viagra) is used to treat erectile dysfunction (impotence; inability to get or keep an erection) in men. Sildenafil (Liqrev, Revatio) is used to improve the ability to exercise in adults (Liqrev, Revatio) and children 1 year of age and older (Revatio) with pulmonary arterial hypertension (PAH; high blood pressure in the vessels carrying blood to the . The normal dose when starting Viagra is 50 mg, as needed. The maximum dose of Viagra is mg each day. Doses above the maximum dose, such as mg per day, will increase the risk of side effects. Sildenafil tablets for pulmonary hypertension come in 10mg and 20mg strengths. The usual adult dose is 20mg taken 3 times a day. Doses for children can range from 10mg to 20mg taken 3 times a day, depending on their weight. Do not take it more than 3 times a day.