Mechanism of action[ edit ] Penile erection during sexual stimulation is caused by increased penile blood flow resulting from the relaxation of penile arteries and the smooth muscle of the corpus cavernosum. Which Works Faster? Just make sure you take it at the same time every day. You can only get it on prescription for erectile dysfunction if you have a specific condition such as multiple sclerosis or a spinal cord injury. In , the Phase 2 clinical studies were initiated for males experiencing ED, then progressed to the Phase 3 trials that supported the drug’s FDA approval. FDA encourages anyone aware of a serious side effect, including consumers or patients, to make a MedWatch report. Ask your pharmacist or doctor for a copy of the manufacturer’s information for the patient.Detailed information Patient copay assistance is not available for Cialis®. Date of Last Review: February 16, Can’t find what you’re looking for? Contact us . Tadalafil is a medicine used to treat erectile dysfunction (ED, also called impotence) and problems with urination caused by an enlarged prostate (benign prostatic hypertrophy or BPH). It is sometimes known by its generic name tadalafil, and sometimes known by its trade name, Cialis. There are also other brands of this medicine available. Tadalafil Brand names: Cialis, Adcirca. Tadalafil. Find out how tadalafil treats erectile dysfunction, pulmonary hypertension and benign prostate enlargement, and how to take it.