Leucovorin can enhance the therapeutic effect and toxicity of fluoropyrimidines such as 5-FU, by increasing the binding of the drug to thymidylate synthase.
Also used to offest the side effects of Methotrexate
Methotrexate is a folate antagonist that works by inhibiting the dihydrofolate reductase enzyme in cells. Leucovorin is a folate derivative that does not need to undergo reduction by the enzyme dihydrofolate reductase for utilization in various one-carbon transfer reactions in the body, such as DNA synthesis.