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. 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). Cialis (tadalafil) is a prescription tablet used for erectile dysfunction and benign prostatic hyperplasia. Learn about dosage, side effects, and more. Cialis (Tadalafil) may treat, side effects, dosage, drug interactions, warnings, patient labeling, reviews, and related medications including drug comparison and health resources. 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. Tadalafil, or generic Cialis, is most commonly used to treat erectile dysfunction (ED). However, it’s also used to treat benign prostatic hyperplasia (BPH) and pulmonary arterial hypertension. 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.