a derivative of folic acid that is used as the calcium salt, leucovorin calcium. Leucovorin is a mixture of the diastereoisomers of the 5-formyl derivative of tetrahydrofolic acid (THF). The biologically active compound of the mixture is the -isomer, known as Citrovorum factor, or -folinic acid. The terms folinic acid and leucovorin generally are used interchangeably. However, the leucovorin product available in the United States is the racemic mixture (ie, contains equal amounts of -folinic acid and -folinic acid). When -folinic acid is used, it is administered at half the dose of leucovorin (the racemic mixture).

Also called citrovorum factor. A metabolically active form of folic acid that has been used in cancer therapy to protect normal cells against methotrexate -- a cancer chemotherapy agent. Also used to treat megaloblastic anemias.

See Leucovorin.