When is leucovorin calcium typically used in conjunction with chemotherapy?

Leucovorin calcium is primarily used in conjunction with chemotherapy to mitigate the effects of methotrexate, especially in cases of high-dose methotrexate therapy. Methotrexate is an antimetabolite that interferes with DNA synthesis by inhibiting the enzyme dihydrofolate reductase. This can lead to toxic effects on normal cells, particularly in the gastrointestinal tract and bone marrow. Leucovorin, which is a form of folic acid, acts as a rescue agent; it helps to replenish the folate stores that methotrexate depletes. By administering leucovorin after methotrexate treatment, it helps to protect normal cells from the toxic effects and promotes recovery, making the chemotherapy regimen safer for the patient.

Other contexts, such as enhancing the effect of antimetabolites or promoting cancer cell proliferation, do not align with the established role of leucovorin. Additionally, increasing drug absorption is not a function of leucovorin; it is specifically used for its protective effects against the harmful side effects of methotrexate therapy. Therefore, its main purpose in this context is as a mitigator of methotrexate toxicity.