Leucovorin is a medication that acts the same way in the body as folic acid. Leucovorin is used to reduce the folic-acid-lowering side effects of methotrexate because it is not affected by methotrexate in the same way that folic acid is. Leucovorin is also used in combination with fluorouracil to treat cancer of the colon.

It is also used to treat a condition known as megaloblastic anemia, which is an anemia that can be caused by sprue (a condition resulting from reduced absorption of nutrients from the stomach into the bloodstream) and can occur during pregnancy and infancy.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are being given this medication, speak to your doctor. Do not stop using this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to use this medication if their doctor has not prescribed it.

When used in combination with fluorouracil for colon cancer, leucovorin is injected into a vein through a specially prepared site on your skin. In this case, leucovorin is always given under the supervision of a doctor familiar with the use of cancer chemotherapy. It is always given under the supervision of a doctor in a hospital or similar setting with access to sterile equipment for preparation.

The recommended dose for this treatment depends on body size. The treatment is often given once a day for 5 days, just before injection with fluorouracil. This treatment can be repeated every 28 days, depending on response to the therapy.

To prevent methotrexate side effects or to treat overdose, leucovorin can either be given as intravenous (into the vein) or intramuscular (into the muscle) injections. The dose is based on body size and is started between 6 and 24 hours of the start of the methotrexate dose. Leucovorin is given every 6 hours until the blood level of methotrexate is in an acceptable range.

For treatment of megaloblastic anemia due to folic acid deficiency, the dose of leucovorin is based on need as determined by your doctor. Taking leucovorin by mouth is preferred over an injectable form; however, if vomiting prevents enough of the medication from being absorbed, an injectable form may be used.

Many things can affect the dose of medication that a person needs, such as body weight, body size, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are using the medication without consulting your doctor.

It is important to use this medication exactly as prescribed by your doctor.

For the oral (by mouth) form of leucovorin, if you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication in a dry place and away from heat and light. Keep this medication out of the reach of children.

Each tablet contains 5 mg of leucovorin as leucovorin calcium. Nonmedicinal ingredients: lactose, magnesium stearate, microcrystalline cellulose, sodium starch glycolate, and starch pregelatinized 1,500.

Do not take leucovorin if you:

• are allergic to leucovorin calcium or any ingredients of the medication
• have pernicious anemia, megaloblastic anemia, or any other anemia that is caused by vitamin B12 deficiency

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

When used for cancer treatment:

• diarrhea
• nausea
• vomiting

Although most of these side effects listed below don't happen very often, they could lead to serious problems if you do not check with your doctor or seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• blistering, peeling, redness, or swelling of the palms of hands or bottoms of feet
• dizziness
• fainting
• seizures
• severe diarrhea
• skin rash, hives, or itching
• sores in the mouth
• unusual infections (symptoms may include fever or chills, severe diarrhea, shortness of breath, prolonged dizziness, headache, stiff neck, weight loss, or listlessness)

Stop taking the medication and seek immediate medical attention if any of the following occur:

• signs of a serious allergic reaction (i.e., abdominal cramps, difficulty breathing, nausea and vomiting, or swelling of the face and throat)
• signs of a severe skin reaction (i.e., rash; blisters or red splotches on skin; blisters in mouth, eyes, ears, or nose; eye irritation; swelling of eyelids; and flu-like symptoms)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin taking a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should take this medication.

Seizures: Leucovorin can decrease the amount of certain seizure medications in the body. As a result, people who take medication for seizures may be at an increased risk of seizures when using leucovorin. If you have seizures or a history of seizure disorder, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Pregnancy: Although leucovorin is considered safe when used during pregnancy, there have not been adequate studies of its use by pregnant women. This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: This medication passes into breast milk. If you are a breast-feeding mother and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children. This medication should only be used for children under the guidance of a doctor who is familiar with the treatment of childhood cancers or blood diseases.

There may be an interaction between leucovorin and any of the following:

• capecitabine
• cotrimoxazole
• fluorouracil
• fosphenytoin
• methotrexate
• phenobarbital (when leucovorin is used in high doses)
• phenytoin (when leucovorin is used in high doses)
• primidone (when leucovorin is used in high doses)
• raltitrexed
• trimethoprim

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications that you are taking. Also tell them about any supplements you take. Since caffeine, decongestants, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.