Know what Cialis is used for, how to take it, and which side effects to expect when starting it. Cialis (tadalafil) is a prescription tablet used for erectile dysfunction and benign prostatic hyperplasia. Learn about dosage, side effects, and more. Cialis relaxes muscles of the blood vessels and increases blood flow to particular areas of the body. Cialis is used to treat erectile dysfunction (impotence) and symptoms of benign prostatic hypertrophy (enlarged prostate). Tadalafil is also available under the brand names Cialis and Adcirca. Typically, your doctor will start by prescribing a low dosage, then adjust it over time to reach the right amount for you. Persons surnamed Cialis objected to Eli Lilly and Company's so naming the drug, but the company has maintained that the drug's trade name is unrelated to the surname. 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. Cialis is an ED medication you can take once daily or as needed before sexual activity. Learn how to take Cialis and avoid side effects. If you take tadalafil for pulmonary arterial hypertension, do not take Cialis® or other PDE5 inhibitors, including sildenafil (Revatio® or Viagra®) or vardenafil (Levitra®). Cialis is a phosphodiesterase 5 (PDE5) inhibitor for the treatment of erectile dysfunction and benign prostatic hyperplasia. Find patient medical information for Tadalafil (Cialis, Adcirca, and others) on WebMD including its uses, side effects and safety, interactions, pictures, warnings, and user ratings.