LEVOLEUCOVORIN INJECTION

12.1 Mechanism of Action High-Dose Methotrexate Therapy Levoleucovorin is the pharmacologically active isomer of 5-formyl tetrahydrofolic acid. Levoleucovorin does not require reduction by the enzyme dihydrofolate reductase in order to participate in reactions utilizing folates as a source of “one-carbon” moieties. Administration of levoleucovorin counteracts the therapeutic and toxic effects of folic acid antagonists such as methotrexate, which act by inhibiting dihydrofolate reductase. Combination with Fluorouracil in Colorectal Cancer Levoleucovorin enhances the therapeutic and toxic effects of fluorouracil. Fluorouracil is metabolized to 5-fluoro-2'-deoxyuridine-5'-monophosphate (FdUMP), which binds to and inhibits thymidylate synthase (an enzyme important in DNA repair and replication). Levoleucovorin is converted to another reduced folate, 5,10-methylenetetrahydrofolate, which acts to stabilize the binding of FdUMP to thymidylate synthase and thereby enhancing the inhibition of t

Contraindications

• • 4 CONTRAINDICATIONS Levoleucovorin is contraindicated in patients who have had severe hypersensitivity to leucovorin products
• • folic acid or folinic acid [see Adverse Reactions ( 6.2 )] . Patients who have had severe hypersensitivity reactions to leucovorin products
• • folic acid or folinic acid. ( 4 )