Refills: See if you can set up automatic refills or order as needed. Finally, we checked customer reviews to better understand user experiences with each platform. This site is intended only for U. Other warning signs of an unsafe online pharmacy include outdated medication, no customer service, or suspiciously low prices. Popular ED medications found online include: Viagra sildenafil : As the first FDA-approved PDE5 inhibitor for ED, sildenafil is taken 30 minutes to four hours before sexual intercourse to help achieve and maintain an erection.Viagra generic form. Viagra is a brand-name medication. How Much Does Medicare Part C Cost? Medically reviewed by Shilpa Amin, M.D., CAQ, FAAFP. FAQs What to consider Cost Overdose Ask your doctor 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. Viagra dosage for erectile dysfunction (ED) is usually milligrams (mg), but those over 65 may start at 25 mg. Your doctor will also need to consider possible drug interactions.