Alternatively, Cialis may be prescribed as an as-needed treatment for ED, to be taken before sexual activity. Oral ED medicines might not work or might be dangerous if you also take any of the following: Nitrate medicines. What side effects can this medication cause? How Effective Is Cialis? Your doctor will probably tell you not to take tadalafil if you are taking nitrates. These include a heart attack, stroke or a serious heart rhythm disorder in the past six months. One of these is PAH.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 . We have good news for you: generic Cialis, used to treat erectile dysfunction (ED) and enlarged prostates, just hit pharmacies. Prices for the generic, known as tadalafil, are more than 50% less than those of brand-name Cialis. As more men are . Cialis and Viagra are phosphodiesterase-5 (PDE5) inhibitors used for treating impotence (erectile dysfunction, or ED).; Adcirca is another brand name of tadalafil.; Common side effects of Cialis and Viagra that are similar include flushing (redness or warmth of the face, neck, or chest), headaches, stomach pain or upset, flu-like symptoms (such as stuffy .