Although not all of these side effects may occur, if they do occur they may need medical attention. FDA encourages anyone aware of a serious side effect, including consumers or patients, to make a MedWatch report. Ask your healthcare professional how you should dispose of any medicine you do not use. Bleeding disorders or Stomach ulcers—Use must be determined by your doctor. After taking a single tablet, some of the active ingredient of Cialis remains in your body for more than 2 days. Emling S. Non—arteritic anterior ischemic optic neuropathy NAION, serious eye condition in one or both eyes, history of—Use with caution.Generic tadalafil has been available since and has proven to be just as effective and safe as the brand name. The drug is available in low daily doses that keep the medication in your system. Cialis (tadalafil) is a type of PDE5 inhibitor that the Food and Drug Administration approved in Like other PDE5 inhibitors, it increases blood flow to the penis. There are two different ways to take Cialis: as needed or daily.