Place the tip of the syringe into you or your child’s mouth and point it towards the cheek. 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 lungs, causing shortness of breath, dizziness, and tiredness. Its effects often last for 4 to 5 hours. Keep out of the reach of children. Sildenafil treats PAH by relaxing the blood vessels in the lungs to allow blood to flow easily. This increased blood flow can cause an erection.Sildenafil (Viagra). This medicine works best when you take it on an empty stomach an hour before sex. The body takes longer to absorb it after a high-fat meal or alcohol. Its . you should know that sildenafil is available under the brand names Liqrev, Revatio, and Viagra. You should only be treated with one of these products at a time. The following . You’ll likely start with a Viagra dose of 50 mg. You’ll typically take Viagra about 1 hour before sex. You can take the drug 30 minutes to 4 hours before you anticipate sexual .