Also tell your doctor if you or any of your family members have or have ever had an eye disease such as retinitis pigmentosa an inherited eye condition that causes loss of vision or if you have ever had sudden severe vision loss, especially if you were told that the vision loss was caused by a blockage of blood flow to the nerves that help you see. Do not stop taking tadalafil without talking to your doctor. BPH is caused by an enlarged prostate. If you are taking tadalafil on a regular schedule, take it at around the same time every day. What special precautions should I follow?Cialis is a prescription medication containing the active ingredient tadalafil. Cialis belongs to a group of medications known as phosphodiesterase-5 (PDE-5) . Cialis comes as oral tablets that are available in four strengths: milligrams (mg), 5 mg, 10 mg, and 20 mg. Recommended dosage for Cialis Typically, . 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 .