It lasts 4 to 5 hours, or longer if you have mild to moderate ED. Box , Mission, KS If your pharmacy does not participate, you may be able to submit a request for a rebate in connection with this Savings Offer. How oral medicines differ Each oral medicine for ED has a slightly different chemical makeup. Common ones include: Flushing of the skin. This medication is taken with or without food an hour before sex. 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. Tadalafil Cialis.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 . Learn more about what VIAGRA® (sildenafil citrate), a prescription treatment for ED. Tell your healthcare provider about all the medicines you take, including prescription and . 25 rows · How long does Viagra last and how soon does it work? View more FAQ.