Tadalafil belongs to a group of medicines, known as phosphodiesterase-5 (PDE-5) inhibitors, which are used to treat erectile dysfunction or pulmonary arterial hypertension. 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. Cialis (tadalafil) is a prescription tablet used for erectile dysfunction and benign prostatic hyperplasia. Learn about dosage, side effects, and more. Learn about the side effects of tadalafil, from common to rare, for consumers and healthcare professionals. Tadalafil is a generic drug prescribed for erectile dysfunction and other conditions. Learn about the drug’s dosages, form, strengths, and more. What Is Tadalafil and How Does It Work? Tadalafil is a phosphodiesterase inhibitor used for treating impotence (erectile dysfunction, or ED), benign prostatic hyperplasia (BPH), and pulmonary arterial hypertension (PAH). Tadalafil is used to treat men who have erectile dysfunction (also called sexual impotence). Tadalafil belongs to a group of medicines called phosphodiesterase 5 (PDE5) inhibitors. Tadalafil relaxes muscles of the blood vessels and increases blood flow to particular areas of the body. Tadalafil under the name of Cialis is used to treat erectile dysfunction (impotence) and symptoms of benign prostatic hypertrophy (enlarged prostate). Learn about tadalafil (Cialis) usage and dosing. Read the latest news and reviews about the drug as well as potential side effects and popular alternatives. Brand names: Cialis, Adcirca. Tadalafil comes only as a tablet you take by mouth. Tadalafil is used to treat the symptoms of benign prostatic hyperplasia (BPH) and erectile dysfunction (ED).