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. Cialis is a phosphodiesterase 5 (PDE5) inhibitor for the treatment of erectile dysfunction and benign prostatic hyperplasia. 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). If you take tadalafil for pulmonary arterial hypertension, do not take Cialis® or other PDE5 inhibitors, including sildenafil (Revatio® or Viagra®) or vardenafil (Levitra®). The maximum recommended dosing frequency is once per day in most patients. CIALIS for use as needed was shown to improve erectile function compared to placebo up to 36 hours following dosing. Therefore, when advising patients on optimal use of CIALIS, this should be taken into consideration. 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 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. 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 Cialis (Tadalafil) may treat, side effects, dosage, drug interactions, warnings, patient labeling, reviews, and related medications including drug comparison and health resources.