The chemical Tadalafil has a designated molecular formula of C22H19N3O4 and a molecular weight of 389.411 g/mol. Synonyms may include: IC 351, GF 196960, ICOS 351, IC351, (6R,12aR)-2,3,6,7,12,12a-Hexahydro-2-methyl-6-(3,4-methylenedioxyphenyl)pyrazino(1',2':1,6)pyrido(3,4-b)indole-1,4-dione, HSDB 7303, Cialis, UNII-742SXX0ICT, Adcirca, Tadalafil Lilly (ChemID). Tadalafil has been assigned a MeSH pharmacological action of: Phosphodiesterase 5 Inhibitor.