Leucovorin is a supportive medication used in cancer care, often in direct partnership with chemotherapy. It is a folate analog, meaning it is a form of folic acid, a B vitamin that cells need for growth and division. Also known as folinic acid, its primary purpose is not to destroy cancer cells itself, but to either protect healthy cells from the effects of certain chemotherapy drugs or to help other chemotherapy drugs work more effectively.
The Role of Leucovorin in Cancer Treatment
Leucovorin performs two distinct functions in cancer therapy, depending on the chemotherapy drug it is paired with. Its most well-known use is as a “rescue” agent following high-dose methotrexate treatment. Methotrexate works by blocking an enzyme that activates folic acid, thereby stopping cell growth and division in both cancerous and healthy cells alike. This action can lead to significant damage to healthy tissues, particularly in the bone marrow and the lining of the digestive tract.
To prevent this damage, leucovorin is administered after the methotrexate has had time to affect the cancer cells, typically within 12 to 24 hours. Leucovorin provides a reduced form of folic acid that healthy cells can readily use without needing the enzyme that methotrexate blocks. This allows the normal cells to resume their functions and recover, effectively “rescuing” them from the chemotherapy’s toxic effects while the cancer cells have already been targeted.
A different function of leucovorin is to enhance the effectiveness of another chemotherapy drug, 5-fluorouracil (5-FU), which is commonly used for cancers like colorectal cancer. In this context, leucovorin is not used for rescue but as a potentiator. It helps 5-FU bind more tightly to an enzyme inside cancer cells called thymidylate synthase. This stronger bond improves the drug’s ability to shut down DNA synthesis in the cancer cells, leading to a more potent anti-cancer effect.
Administration and Dosage
The method of administering leucovorin is tailored specifically to the patient and the chemotherapy regimen they are receiving. It can be given either as an intravenous (IV) infusion or as oral tablets. The choice between IV and oral administration often depends on the specific cancer treatment protocol and whether the patient can absorb the medication properly through their digestive system. For instance, IV administration is often preferred if a patient is experiencing nausea or vomiting.
Healthcare providers determine the precise dosage and timing of leucovorin based on several factors, including the type and dose of chemotherapy being used. When used as a rescue agent with methotrexate, the timing is particularly important. Doses are typically started within a specific window after the methotrexate infusion and may continue every six hours until blood tests confirm that methotrexate levels have fallen to a safe range.
Adherence to the prescribed schedule is important for both safety and effectiveness. Missing a dose or taking it at the wrong time can diminish its protective effects, potentially exposing healthy cells to harm. Patients must follow their oncologist’s directions and communicate immediately if they are unable to keep an appointment or take the medication as scheduled.
Potential Side Effects and Management
While leucovorin itself rarely causes significant side effects, it can influence the side effects of the chemotherapy it is paired with. When used with 5-fluorouracil, it can sometimes increase the side effects of that medication, such as diarrhea or mouth sores. Patients should monitor for these symptoms and report them to their care team if they become severe or do not improve.
The most common reactions that patients might experience are generally mild and can include nausea, vomiting, or diarrhea. These are often manageable and may be related to the accompanying chemotherapy. It is important for patients to communicate with their healthcare team about any persistent digestive issues so they can receive appropriate supportive care.
Although rare, more serious allergic reactions to leucovorin can occur. Symptoms that require immediate medical attention include hives, itching, rash, difficulty breathing, or swelling of the face, lips, or tongue. Any sign of a potential allergic reaction should be reported to a healthcare provider immediately.