Tadalafil will make these symptoms less severe and reduce the chance that prostate surgery will be needed. Your doctor or other health care professional can recommend one for you based on these factors, other health conditions you have and any other medicines you take. You can take this medicine with or without food 30 minutes before sex, depending on the dose. Ask your pharmacist for a list of the ingredients. This includes prescription or nonprescription over-the-counter [OTC] medicines and herbal or vitamin supplements. Do not take a double dose or more than one dose per day to make up for a missed one.How Cialis Works. Tadalafil and other PDE5 inhibitors primarily work by inducing muscle relaxation. Tadalafil stops the breakdown of a chemical responsible for relaxing muscles. In ED and PAH, the drug targets muscle cells in blood vessels. When the blood vessel muscle cells relax, this expands the vessel and increases blood flow; this . 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. Tadalafil (Cialis) is available both as brand-name and generic tablets. Common side effects of this medication include headache and indigestion. Tadalafil .