Ketamine see a doctor. Sexual activity may be a strain on your heart, especially if you have heart disease. Take all of the tablets for your daily dose at one time each day; do not divide the tablets to take as separate doses. What should I do if I forget a dose? Ask your pharmacist or doctor for a copy of the manufacturer’s information for the patient. ED occurs more frequently in older men.Cialis is a prescription medication containing the active ingredient tadalafil. Cialis belongs to a group of medications known as phosphodiesterase-5 (PDE-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 . 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? .