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 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). 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. Tadalafil (Eqv-Cialis) is used in adult men to treat erectile dysfunction (impotence) and symptoms of benign prostatic hypertrophy (enlarged prostate). Tadalafil (Eqv-Cialis) can also be used in men and women to treat pulmonary arterial hypertension (PAH) and improve exercise capacity. Tadalafil is a generic drug prescribed for erectile dysfunction and other conditions. Learn about the drug’s dosages, form, strengths, and more. 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 is FDA -approved for males as a therapy to treat and prevent symptoms of benign prostatic hyperplasia, such as urinary urgency, hesitancy, weak stream, dribbling, and incontinence.