Tadalafil is a phosphodiesterase type 5 (PDE5) inhibitor, widely known by the brand name Cialis. It is used for the treatment of erectile dysfunction (ED) and also for the treatment of pulmonary hypertension. Molecular structure of tadalafil The chemical name for tadalafil is 1,2,3,4-tetrahydro-β-carboline-6-carboxamide, and its official chemical formula is C₂₂H₁₉N₃O₄. This molecule has several characteristic chemical structures: Molecular Mechanism of Action Tadalafil inhibits the PDE5 enzyme from degrading cGMP (cyclic guanosine monophosphate). cGMP aids erection by promoting smooth muscle relaxation and increasing blood flow,...