Medicines that you take by mouth are called oral medicines. These include a heart attack, stroke or a serious heart rhythm disorder in the past six months. Tadalafil Cialis. This medication is taken with or without food an hour before sex. These small differences affect the way each medication works, such as how quickly it takes effect and wears off, and the possible side effects.Viagra Connect is the first erectile dysfunction medicine in the UK to be sold without the need for a prescription, which means you can order Viagra Connect discreetly online or buy in-store without the need to make an appointment with your GP. How does Viagra . 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 . For further information, call , visit , or write: Viatris Inc., P.O. Box , Mission, KS See risks & benefits. Learn more about what VIAGRA® (sildenafil citrate), a prescription treatment for ED.