CIALIS contains the active substance tadalafil which belongs to a group of medicines called phosphodiesterase type 5 inhibitors. CIALIS 5 mg is used to treat adult men with:-erectile dysfunction. This is when a man cannot get, or keep a hard, erect penis suitable for sexual activity. CIALIS has been shown to significantly improve the ability of obtaining a hard erect penis suitable for sexual activity. Following sexual stimulation CIALIS works by helping the blood vessels in your penis to relax, allowing the flow of blood into your penis. The result of this is improved erectile function. CIALIS will not help you if you do not have erectile dysfunction. It is important to note that CIALIS for the treatment of erectile dysfunction does not work if there is no sexual stimulation. You and your partner will need to engage in foreplay, just as you would if you were not taking a medicine for erectile dysfunction. -urinary symptoms associated with a common condition called benign prostatic hyperplasia. This is when the prostate gland gets bigger with age. Symptoms include difficulty in starting to pass water, a feeling of not completely emptying the bladder and a more frequent need to pass water even at night. CIALIS improves blood flow to, and relaxes the muscles of, the prostate and bladder which may reduce symptoms of benign prostatic hyperplasia. CIALIS has been shown to improve these urinary symptoms as early as 1-2 weeks after starting treatment.