--- - "" - "" - "" - "" - "" - "" - "" - "" - "" - "" - [email protected] - [email protected] - "" - "" - "" - "Cialis (tadalafil) is a discriminatory inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase archetype 5. Tadalafil cialis without a doctors prescription has the empirical formula C22H19N3O4 representing a molecular rig of 389.41. The structural formula is:"