Your doctor will probably tell you not to take tadalafil if you are taking street drugs containing nitrates. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. This is high blood pressure that occurs in the main artery that carries blood from the right side of the heart the ventricle to the lungs. It works to treat erectile dysfunction by increasing blood flow to the penis during sexual stimulation. John’s wort. The enlarged prostate interferes with the normal flow of urine from the bladder and urinary tract, resulting in lower urinary tract symptoms, such as trouble urinating.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 .  · Cialis (tadalafil) is prescribed to treat erectile dysfunction and symptoms of benign prostatic hyperplasia. It comes as a tablet that’s taken as needed or once per . Cialis is a prescription medication containing the active ingredient tadalafil. Cialis belongs to a group of medications known as phosphodiesterase-5 (PDE-5) .