One of these is PAH. Precautions It is important that you tell all of your doctors that you take tadalafil. Tadalafil was found to have similar benefits for lower urinary tract symptoms as the usually prescribed tamsulosin. Call your doctor for medical advice about side effects. Do not take other medicines unless they have been discussed with your doctor. Take the medicine at the same time each day, with or without food.Tadalafil is in a class of medications called phosphodiesterase (PDE) inhibitors. It works to treat erectile dysfunction by increasing blood flow to the penis during sexual stimulation. This increased blood flow can cause an erection. Tadalafil treats PAH by relaxing the blood vessels in the lungs to allow blood to flow more easily. 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 . Generic Cialis is called tadalafil, which is the active ingredient in Cialis. Cialis is Food and Drug Administration (FDA) approved to treat erectile dysfunction (ED) and benign prostatic.