Tadalafil is a phosphodiesterase type 5 (PDE5) inhibitor. A PDE5 inhibitor is a medication that blocks the action of a substance known as cyclic guanosine monophosphate (cGMP), in the cells that form part of the blood supply to the penis.
The muscles of the arteries in the walls of the lungs also contain PDE5, which is why tadalafil can also help with pulmonary hypertension treatment. Cialis comes in yellow, film-coated and almond shaped tablets in 5, 10 and 20 milligram (mg) doses.
Cialis was approved by the United States Food and Drug Administration (FDA) in 2003 for the treatment of erectile dysfunction. In May 2009 tadalafil received approval for the treatment of pulmonary arterial hypertension.