Before taking tadalafil, tell your doctor and pharmacist if you are allergic to tadalafil, any other medications, or any of the ingredients in tadalafil tablets. Ketamine see a doctor. Answered By: Dr. You should only be treated with one of these products at a time. For further information contact your pharmacist or Eli Lilly and Company directly. Follow your doctor’s directions carefully, and ask your doctor or pharmacist to explain any part you do not understand.Cialis and generic tadalafil are available with a prescription only. There is no OTC version, though there have been efforts in recent years to develop a . 1. What is Cialis used to treat? Cialis is approved for the treatment of men who experience difficulty having and maintaining an erection (impotence). 2. How does Cialis work? . You need a prescription for Cialis or its generic counterpart, Tadalafil. Both items are useful in the treatment of an enlarged prostate, erectile dysfunction, and benign prostatic .