Place the tip of the syringe into you or your child’s mouth and point it towards the cheek. However, the dose is usually not more than 80 mg 3 times a day. If you experience a prolonged or painful erection for 4 hours or more, contact your doctor immediately. To use the oral liquid: Shake the bottle well for at least 10 seconds before each use. Your doctor or other health care professional can recommend one for you based on these factors, other health conditions you have and any other medicines you take. If you see air bubbles in the syringe, repeat the steps. Common ones include: Flushing of the skin.Sildenafil (Viagra, Revatio) is a moderately priced drug used to treat erection problems in men. It is also used to treat pulmonary arterial hypertension, a serious heart and lung . Typical dosing for Sildenafil (Viagra) The typical dose is to take 50 mg of sildenafil (Viagra) by mouth, about 1 hour before sex, as needed. The maximum recommended dose is mg. Don’t take sildenafil (Viagra) more than once daily (at any dose). Written by Brian Leonard, PharmD, BCACP, BCGP.  · Viagra; Descriptions. Sildenafil is used to treat men who have erectile dysfunction (also called sexual impotence). Sildenafil belongs to a group of medicines called phosphodiesterase 5 (PDE5) inhibitors. However the dose is usually not more than 40 mg 3 times a day. Children 1 year of age and older weighing 20 to 45 kg—20 mg 3 times a day.