Name Cialis Synonyms (6R,12aR)-6-(1,3-Benzodioxol-5-yl)-2,3,6,7,12,12a-hex ahydro-2-methyl-pyrazino[1',2':1,6]pyrido[3,4-b]indole-1,4-dione; Tadalafil Molecular Formula C22H19N3O4 Molecular Weight 389.40 CAS Registry Number 171596-29-5