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. Never purchase ED medications from a site or service that doesn’t require a prescription and medical documentation. Blood pressure: Tell your doctor if you are taking medications to treat high blood pressure. The products discussed in this site may have different product labeling in different countries. Terms and conditions of use.The Savings Offer and Program expire on 12/31/ For further information, call , visit , or write: Viatris Inc., P.O. Box , Mission, KS . Sildenafil belongs to a group of medications called phosphodiesterase type 5 inhibitors. It is used for the treatment of erectile dysfunction (male impotence). It helps to achieve and . Side Effects. In addition to its desired action, this medication may cause some side effects, notably: it may cause headaches; it may cause indigestion; it may cause redness of the .