Other warning signs of an unsafe online pharmacy include outdated medication, no customer service, or suspiciously low prices. How oral medicines differ Each oral medicine for ED has a slightly different chemical makeup. You can take it in a small dose daily or in a larger dose as needed. When oral medications might not be safe Check with your health care team before you take any medicine for erectile dysfunction. Levitra vardenafil : This medication is taken one hour before sex and can last up to 24 hours.Sildenafil (Viagra). Tadalafil (Cialis). Vardenafil. These medicines are called PDE5 inhibitors. They enhance the effects of a chemical the body makes that relaxes . Examples of Viagra’s more commonly reported side effects include: headache. flushing (temporary warmth, redness, or deepening of skin color) stuffy nose. . CHOOSE BRAND-NAME VIAGRA. The original little blue pill prescribed by doctors for over 20 years. Clinically proven to treat men with erectile dysfunction (ED) Ongoing .