These medicines all work well for ED. Sexual activity may be a strain on your heart, especially if you have heart disease. Take sildenafil as needed before sexual activity. Children 1 year of age and older weighing 20 to 45 kg—20 mg 3 times a day. This will increase the supply of blood to the lungs and reduce the workload of the heart.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 (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 . Optum Store Sildenafil If you are experiencing the symptoms of erectile dysfunction (ED), you may have considered using Viagra or a similar ED medication as a possible .