"experimental"@en . "The active metabolite of FOLIC ACID. Leucovorin is used principally as its calcium salt as an antidote to folic acid antagonists which block the conversion of folic acid to folinic acid. [PubChem]"@en . . . . . . . . . . . . . . . . . . . . . . . . . . "5-Formyl-5,6,7,8-Tetrahydrofolate"@en . . . . . . . . . . . "58-05-9"@en . .