Cialis is most commonly used to treat erectile dysfunction and impotence, which is when a man struggles to maintain an erection or cannot get erect at all. It's also sometimes prescribed for an enlarged prostate.
Tadalafil is the active ingredient of Cialis. It improves blood flow to the penis so that a man can get an erection for sexual activity.
Depending on how your doctor prescribes the medication, you might take it as needed before sex or every day. If you take it as needed, the effects may last up to 36 hours.