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 (tadalafil) is a prescription medication for erectile dysfunction (ED). It usually starts working within 30 minutes but can take up to 2 hours to fully set in. Be sure to follow your recommended Cialis dosage, whether you’re taking it every day or as needed. Cialis is a phosphodiesterase 5 (PDE5) inhibitor for the treatment of erectile dysfunction and benign prostatic hyperplasia. 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. Cialis (Tadalafil) may treat, side effects, dosage, drug interactions, warnings, patient labeling, reviews, and related medications including drug comparison and health resources. 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). 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 popular ED medication. Find out everything you need to know about this doctor-prescribed medication including usage, effectiveness, safety considerations, and where to buy online. 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.