Cialis is the brand name for tadalafil, a drug used to treat erectile dysfunction. It is similar to Viagra and Levitra. Under the brand name Adcirca, tadalafil is used for pulmonary arterial hypertension.
Cialis increases blood flow to the penis, and this enables a man to achieve an erection. It does not lead to sexual arousal. It should be used with caution, and only under medical supervision.