Continue to take tadalafil even if you feel well. If you are taking tadalafil on a regular schedule, take it at around the same time every day. If you are taking tadalafil for erectile dysfunction on a regular schedule, take the missed dose as soon as you remember it. These include itraconazole Sporanox, Tolsura , ketoconazole Extina, Ketozole, others and ritonavir Norvir. When choosing one, tell your doctor or other health care professional what your preferences are, such as cost, ease of use, how long the drug’s effects last and side effects. Alternatively, Cialis may be prescribed as an as-needed treatment for ED, to be taken before sexual activity. Erectile dysfunction is a condition where the penis does not harden and expand when a man is sexually excited, or when he cannot keep an erection.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 day, depending on . The four main medicines taken by mouth for erectile dysfunction are: Avanafil (Stendra). Sildenafil (Viagra). Tadalafil (Cialis). Vardenafil. These medicines are called PDE5 . Cialis is used for the treatment of erectile dysfunction (ED). It increases blood flow to the penis following sexual stimulation and allows men to keep an erection hard enough for .