Folinic acid (INN) or leucovorin (USAN), generally administered as calcium or sodium folinate (or leucovorin calcium/sodium), is an adjuvant used in cancer chemotherapy involving the drug methotrexate. It is also used in synergistic combination with the chemotherapy agent 5-fluorouracil.
Levofolinic acid and its salts are the enantiopure drugs (in this case, the levo form), and are the only molecules that are biologically active. They are configurated S at the remaining asymmetric carbon atom (see below).
Folinic acid was first discovered in 1948 as citrovorum factor and occasionally is still called by that name. Folinic acid should be distinguished from folic acid (Vitamin B9). However, folinic acid is a vitamer for folic acid, and has the full vitamin activity of this vitamin.
Read more about Folinic Acid: History of Discovery As Citrovorum Factor, Mechanism of Action, Therapeutic Use, Note On Administration