Tadalafil is in a class of medications called phosphodiesterase PDE inhibitors. What should I talk to my doctor about when considering if Cialis is right for me? It can also interact with many medicines, particularly nitrates used in some types of heart disease and blood pressure medicines. What if I am taking other drugs? Tadalafil comes as a tablet to take by mouth.Tadalafil (Cialis) 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). Tadalafil works by helping to relax the blood vessels in the penis, allowing blood to flow into the penis, and causing an erection. 4. Bottom Line. Cialis is used to treat erectile dysfunction (ED) and to reduce symptoms of benign prostatic hyperplasia (BPH). One ‘as needed’ tablet lasts for 36 hours or Cialis is available as a lower dosage that can be taken on a daily basis, eliminating the need to ‘plan for sex’. 5. Tadalafil (Cialis) is used to treat erectile dysfunction (ED, impotence; inability to get or keep an erection), and the symptoms of benign prostatic hyperplasia (BPH; an enlarged prostate) which include difficulty urinating (hesitation, dribbling, weak stream, and incomplete bladder emptying), painful urination, and urinary frequency and urgency in adult men.