These include a heart attack, stroke or a serious heart rhythm disorder in the past six months. How oral medicines differ Each oral medicine for ED has a slightly different chemical makeup. Medicines that you take by mouth are called oral medicines. Can I buy any other ED medications over the counter? Oral ED medicines might not work or might be dangerous if you also take any of the following: Nitrate medicines. Severe liver disease. When oral medications might not be safe Check with your health care team before you take any medicine for erectile dysfunction.Is there an over-the-counter Viagra? Viagra is only available with a prescription in the United States, Canada, and most other countries. Viagra is sold under the generic name sildenafil. The four main medicines taken by mouth for erectile dysfunction are: Avanafil (Stendra). Sildenafil (Viagra). Tadalafil (Cialis). Vardenafil. These medicines are called PDE5 inhibitors. They enhance the effects of a chemical the body makes that relaxes muscles in the penis, called nitric oxide. Some over-the-counter (OTC) supplements may help with erectile dysfunction, such as L-arginine in combination with pycnogenol, Korean red ginseng (also called panax ginseng), Yohimbe, Carnitine (propionyl-L-carnitine), and Dehydroepiandrosterone (DHEA).