Cialis is not recommended for people taking any form of nitroglycerin because the combination may lower blood pressure to an unsafe level. This is high blood pressure that occurs in the main artery that carries blood from the right side of the heart the ventricle to the lungs. Tadalafil is in a class of medications called phosphodiesterase PDE inhibitors. In trials investigating Cialis, the majority of participants receiving the drug experienced a significant improvement in ED and maintained an erection. You’ll soon start receiving the latest Mayo Clinic health information you requested in your inbox.Cialis is available in a generic version. Keep reading for specific information about the dosage of Cialis, including its strengths and how to take the medication. For a comprehensive look at. Tadalafil is a medicine used to treat erectile dysfunction (ED, also called impotence) and problems with urination caused by an enlarged prostate (benign prostatic hypertrophy or BPH). It is sometimes known by its generic name tadalafil, and sometimes known by its trade name, Cialis. There are also other brands of this medicine available. Tadalafil (Cialis) is taken by mouth either as needed before sexual activity or once daily for erectile dysfunction (ED).It’s also taken once daily to treat symptoms from an enlarged prostate (benign prostatic hyperplasia, or BPH).Tadalafil (Cialis) is available both as brand-name and generic tablets. Common side effects of this medication include .