leucovorin

(lü′käv·ə·rən)

(pharmacology) Folinic acid used as a calcium salt to counteract the toxic effects of folic acid antagonists and for treatment of megaloblastic anemias.

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Key Terms: Folic acid.

Definition

Leucovorin (also known as Wellcovorin and citrovorum factor or folinic acid) is a drug that can be used either to protect healthy cells from chemotherapy or to enhance the anti-cancer effect of chemotherapy.

Purpose

Leucovorin is most often used in cancer patients undergoing either methotrexate or fluorouracil chemotherapy. Methotrexate is used to treat a wide range of cancers including breast cancer, head and neck cancers, acute leukemias, and Burkitt's lymphoma. Fluorouracil is used in combination with leucovorin to treat colorectal cancer. When leucovorin and methotrexate are used together, this therapy often is called leucovorin rescue because leucovorin rescues healthy cells from the toxic effects of methotrexate. In patients with colorectal cancer, however, leucovorin increases the anti-cancer effect of fluorouracil.

Leucovorin also is used to treat megaloblastic anemia, a blood disorder in which red blood cells become larger than normal, and to treat accidental overdoses of drugs such as methotrexate.

Description

Leucovorin is a faster acting and stronger form of folic acid, and has been used for several decades. Folic acid also is known as vitamin B9, and is needed for the normal development of red blood cells. In humans, dietary folic acid must be reduced metabolically to tetrahydrofilic acid (THFA) to exert its vital biochemical functions. The coenzyme THFA and its subsequent other cofactors participate in many important reactions including DNA synthesis.

Leucovorin Rescue

Some chemotherapy drugs, such as methotrexate (Mexate, Folex), work by preventing cells from using folic acid. Methotrexate therapy causes cancer cells to develop a folic acid deficiency and die. However, normal cells also are affected by folic acid deficiency. As a result, patients treated with drugs such as methotrexate often develop blood disorders and other toxic side effects. When these patients are given leucovorin, it goes into normal cells and rescues them from the toxic effects of the methotrexate. Leucovorin cannot enter cancer cells, however, and they continue to be killed by methotrexate. Leucovorin also works by rescuing healthy cells in patients who take an accidental overdose of drugs similar to methotrexate.

Combination Therapy

Patients with colorectal cancer frequently are treated with fluorouracil (Adrusil). Fluorouracil, commonly called 5-FU, is effective, but only works for a short time once it is in the body. Leucovorin enhances the effect of fluorouracil by increasing the time that it stays active. As a result, the combination of the two drugs produces a greater anti-cancer effect than fluorouracil alone.

Recommended Dosage

Leucovorin can be given as an injection, intravenously, or as oral tablets. For rescue therapy, leucovorin usually is given intravenously or orally within 24 hours of methotrexate treatment. Dosage varies from patient to patient. When used in combination with fluorouracil, leucovorin is given to the patient intravenously first, followed by fluorouracil treatment. To treat unintentional folic acid antagonist overdose, leucovorin is usually given intravenously as soon as possible after the overdose. Patients with megaloblastic anemia receive oral leucovorin.

Precautions

Patients with anemia, or any type of blood disorder, should tell their doctors. Leucovorin can treat only anemia caused by folic acid deficiency. Patients with other types of anemia should not take leucovorin. The effect of leucovorin on the fetus is not known, and it is not known if the drug is found in breast milk. Leucovorin should therefore be used with caution during pregnancy. Elderly patients treated with leucovorin and fluorouracil for advanced colorectal cancer are at greater risk for developing severe side effects.

Side Effects

The vast majority of patients do not experience side effects from leucovorin therapy. Side effects are usually caused by the patient's chemotherapy, not by leucovorin. In rare cases, however, some patients can develop allergic reactions to the drug. These include skin rash, hives, and itching. In 2004, Swiss researchers found that oral desensitization may work in cases of severe allergic reaction to leucovorin.

Interactions

Although there are no listed drug interactions for leucovorin, patients should tell their doctors about any over the counter or prescription medication they are taking, particularly medication that can cause seizures.

Resources

Periodicals

"Oral Desensitization May Work in Some Cases of Allergy to Leucovorin." Drug Week November 14, 2003: 128.

—Alison McTavish, M.Sc.; Teresa G. Odle

The synthetic (racemic) 5-formyl derivative of folic acid; more stable to oxidation than folic acid itself, and commonly used in pharmaceutical preparations. Also known as folinic acid.

Chemical formula:

Drug Forms:
• Leucovorin Calcium Oral tablet (below)
• Leucovorin Calcium Solution for injection

Español:
• Leucovorina Cálcica, Tableta oral
• Leucovorina Cálcica, Solución para inyección

Leucovorin Calcium Oral tablet

What is this medicine?

LEUCOVORIN (loo koe VOR in) is used to prevent or to treat the harmful effects of some medicines.
 
This medicine may be used for other purposes; ask your health care provider or pharmacist if you have questions.

What should I tell my health care provider before I take this medicine?

They need to know if you have any of these conditions:
•anemia from low levels of vitamin B-12 in the blood
•frequent vomiting and diarrhea
•an unusual or allergic reaction to leucovorin, folic acid, other medicines, foods, dyes, or preservatives
•pregnant or trying to get pregnant
•breast-feeding

How should I use this medicine?

Take this medicine by mouth with a glass of water. Follow the directions on the prescription label. Take your doses at regular intervals. Do not take your medicine more often than directed. It is very important to take this medicine exactly how it is prescribed. Do not stop taking except on your doctor's advice even if you feel better.

Talk to your pediatrician regarding the use of this medicine in children. Special care may be needed.

Overdosage: If you think you have taken too much of this medicine contact a poison control center or emergency room at once.
NOTE: This medicine is only for you. Do not share this medicine with others.

What if I miss a dose?

If it is almost time for your next dose, take only that dose. Do not take double doses. Each dose of this cough medicine should be taken at least 4 hours apart from the previous dose. Do not take more frequently than how it was prescribed by your health care professional.

What may interact with this medicine?

•capecitabine
•fluorouracil
•phenobarbital
•phenytoin
•primidone
•trimethoprim-sulfamethoxazole

This list may not describe all possible interactions. Give your health care provider a list of all the medicines, herbs, non-prescription drugs, or dietary supplements you use. Also tell them if you smoke, drink alcohol, or use illegal drugs. Some items may interact with your medicine.

What should I watch for while using this medicine?

Your condition will be monitored carefully while you are receiving this medicine. You will need important blood work done while you are taking this medicine.

Tell your doctor if you have nausea or vomiting regularly.

What side effects may I notice from receiving this medicine?

Side effects that you should report to your doctor or health care professional as soon as possible:
•allergic reactions like skin rash, itching or hives, swelling of the face, lips, or tongue
•breathing problems

This list may not describe all possible side effects. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Where should I keep my medicine?

Keep out of the reach of children.

Store at room temperature between 15 and 25 degrees C (59 and 77 degrees F). Protect from light and moisture. Throw away any unused medicine after the expiration date.

Last updated: 7/1/2002

Important Disclaimer: The drug information provided here is for educational purposes only. It is intended to supplement, not substitute for, the diagnosis, treatment and advice of a medical professional. This drug information does not cover all possible uses, precautions, side effects and interactions. It should not be construed to indicate that this or any drug is safe for you. Consult your medical professional for guidance before using any prescription or over the counter drugs.