Cialis 5mg Tadalafil is a treatment for adult men with erectile dysfunction. This is when a man cannot get, or keep a hard, erect penis… Cialis 5mg Tadalafil is a treatment for adult men with erectile dysfunction. This is when a man cannot get, or keep a hard, erect penis suitable for sexual activity. Tadalafil has been shown to significantly improve the ability to obtain a hard erect penis suitable for sexual wellness.Cialis (Tadalafil) is used to treat male sexual function problems (impotence or erectile dysfunction-ED). In combination with sexual stimulation, tadalafil works by increasing blood flow to the penis to help a man get and keep an erection