Remove the syringe from the bottle. Push the plunger of the syringe, then insert the tip into the bottle while holding the bottle upright on a flat surface. Your doctor may adjust your dose as needed and tolerated. There is a problem with information submitted for this request. If too much is used, the chance of side effects is increased.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 . Place the tip of the syringe into you or your child’s mouth and point it towards the cheek. This medicine usually begins to work for erectile dysfunction within 30 minutes after . Sildenafil works on the PDE5 enzyme in the lungs to relax the blood vessels. This will increase the supply of blood to the lungs and reduce the workload of the heart. This .