It lasts 4 to 5 hours, or longer if you have mild to moderate ED. Viagra is typically taken at a dose of 50mg about one hour before sex. If you experience chest pain, dizziness, or nausea during sex, seek immediate medical help. They include dutasteride Avodart, Jalyn and finasteride Propecia, Proscar. If you have an erection that lasts more than 4 hours, get medical help right away.Q&A. Drug Images. What is Viagra? If you have erectile dysfunction (ED), your doctor may recommend that you take Viagra. It’s a prescription drug that’s used in adult males* . For professionals. Drug Images. What is Viagra? Viagra is a brand-name prescription drug that’s approved to treat erectile dysfunction (ED). With ED, you’re unable to have or maintain an. AdEnjoy low prices and get fast, free delivery with Prime on millions of products. Discover new arrivals & latest discounts in male ed meds from your favorite brands.