Sudden vision loss in one or both eyes can be a sign of a serious eye problem called non-arteritic anterior ischemic optic neuropathy NAION. To use the oral liquid: Shake the bottle well for at least 10 seconds before each use. What should I do if I forget a dose? Side effects Side effects of oral ED medicines are often mild. These small differences affect the way each medication works, such as how quickly it takes effect and wears off, and the possible side effects.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 . Sildenafil relaxes muscles of the blood vessels and increases blood flow to particular areas of the body. Sildenafil under the name Viagra is used to treat erectile dysfunction . 25 milligrams (mg) 50 mg mg Typical dosages The following information describes commonly recommended dosages for ED. However, be sure to take the dosage your .