The active metabolite of Folic acid, Pteroyl-D-glutamic acid is used principally as its calcium salt as an antidote to folic acid antagonists which block the conversion of folic acid to folinic acid. Folic acid, a water-soluble B-complex vitamin, is found in foods such as liver, kidneys, yeast, and leafy, green vegetables. Folic acid is used to diagnose folate deficiency and to treat topical sprue and megaloblastic and macrocytic anemias, hematologic complications resulting from a deficiency in folic acid. A member of the vitamin B family that stimulates the hematopoietic system. It is present in the liver and kidney and is found in mushrooms, spinach, yeast, green leaves, and grasses (poaceae). Folic acid is used in the treatment and prevention of folate deficiencies and megaloblastic anemia.
belongs to the class of organic compounds known as tetrahydrofolic acids. These are heterocyclic compounds based on the 5,6,7,8-tetrahydropteroic acid skeleton conjugated with at least one L-glutamic acid unit.
Following oral administration, leucovorin is rapidly absorbed. The apparent bioavailability of leucovorin was 97% for 25 mg, 75% for 50 mg, and 37% for 100 mg.
Mechanism of Toxicity
As leucovorin is a derivative of folic acid, it can be used to increase levels of folic acid under conditions favoring folic acid inhibition (following treatment of folic acid antagonists such as methotrexate). Leucovorin enhances the activity of fluorouracil by stabilizing the bond of the active metabolite (5-FdUMP) to the enzyme thymidylate synthetase.
Metabolism
Hepatic and intestinal mucosal, the main metabolite being the active 5-methyltetrahydrofolate. Leucovorin is readily converted to another reduced folate, 5,10-methylenetetrahydrofolate, which acts to stabilize the binding of fluorodeoxyridylic acid to thymidylate synthase and thereby enhances the inhibition of this enzyme.
Half Life: 6.2 hours
No indication of carcinogenicity to humans (not listed by IARC).
Uses/Sources
For the treatment of osteosarcoma (after high dose methotrexate therapy). Used to diminish the toxicity and counteract the effects of impaired methotrexate elimination and of inadvertent overdosages of folic acid antagonists, and to treat megaloblastic anemias due to folic acid deficiency. Also used in combination with 5-fluorouracil to prolong survival in the palliative treatment of patients with advanced colorectal cancer. Used in cancer chemotherapy involving the drug methotrexate.
Minimum Risk Level
Not Available
Health Effects
Should not be administered intrathecally as this may produce severe adverse effects or even death when administered. [Wikipedia].
Allergic sensitization (<1%), including anaphylactoid reactions
Symptoms
Excessive amounts of leucovorin may nullify the chemotherapeutic effect of folic acid antagonists.
