In this guide, we aim to cover everything you need to know about buying Cialis online. Ensure that the product description mentions this. Tadalafil was approved in in the United States for the treatment of pulmonary arterial hypertension [28] and is under regulatory review in other regions for this condition. Cialis was also investigated in combination with finasteride, another BPH medication, in another trial. The drug is approved for use in adults. Also, look into whether expediting is offered. Tadalafil is the active ingredient in a branded drug called Cialis. · Below, we’ll detail nine of the most common tadalafil interactions to keep in mind. 1. Nitrates. Nitrates are used to treat and prevent angina (chest pain) caused by heart disease. Examples include nitroglycerin (Nitrostat), isosorbide mononitrate (Monoket), and isosorbide dinitrate (Isordil). CVS Pharmacy. $ retail. Save 67%. $ Get free savings. Select this if your pharmacy isn’t listed above. Other pharmacies. $ 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 .