Daily doses are often between 2. In addition, ED is extremely common. If it is not treated right away, priapism can permanently damage your penis sudden vision loss in one or both eyes. There is also the option to take Cialis as needed. You are encouraged to report adverse events related to Viatris products by calling U. 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. Your healthcare provider can help you determine the right dosage for you.This means that 4 hours after you take a dose, your body has cleared half of the dose. In most cases, it takes about 5 half-lives for your body to completely remove a drug from your system. So.  · Generic name: sildenafil (oral) [ sil-DEN-a-fil ] Brand names: Revatio, Viagra Drug classes: Agents for pulmonary hypertension, Impotence agents Medically reviewed . 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 .