Cialis, also known as tadalafil, is a common medication used to treat the symptoms of erectile dysfunction, and in some cases to treat benign prostatic hyperplasia (BPH). Tadalafil belongs to a class of medications called PDE5 inhibitors, and comes in 2.5mg, 5mg, 10mg, and 20mg strengths. If your doctor has recommended Cialis for your ED symptoms, it's important to be educated on the medication. Learn more about Cialis for ED, dosages, side effects and interactions by reading our articles today.