What This Drug Is Used For:

• In combination with fluoruracil to treat cancers such as; colon and rectal, head and neck, esophageal, and other cancers of the gastrointestinal tract. 
• As an antidote to effects of certain chemotherapy drugs such as methotrexate.
• Treatment of megaloblastic anemia when folic acid deficiency is present.

How This Drug Is Given:

• As an injection or short infusion through the vein (intravenous, IV). 
• As a tablet by mouth.   
• As an injection into the muscle (intramuscular, IM). 

Side Effects:

Important things to remember about the side effects of leucovorin:

• The side effects with treatment of leucovorin are likely attributable to other chemotherapy medications being given in combination with leucovorin. 
• When given in combination with fluorouracil (5-FU) the side effects of fluorouracil may be more severe. 
• When given in combination with methotrexate, leucovorin is given to lessen the side effects of methotrexate.

The following are possible side effects of Folinic Acid:

• Allergic reaction: rash, itching, facial flushing.  
• Nausea and vomiting 

When to contact your doctor or health care provider:

Contact your health care provider immediately, day or night, if you should experience any of the following symptoms:

• Shortness of breath, wheezing, difficulty breathing, closing up of the throat, swelling of facial features, hives (possible allergic reaction).

Always inform your health care provider if you experience any unusual symptoms.

Precautions:

• Before starting leucovorin treatment, make sure you tell your doctor about any other medications you are taking (including prescription, over-the-counter, vitamins, herbal remedies, etc.). Do not take aspirin, products containing aspirin unless your doctor specifically permits this.
• Inform your health care professional if you are pregnant or may be pregnant prior to starting this treatment.    
• For both men and women: Do not conceive a child (get pregnant) while taking leucovorin. Barrier methods of contraception, such as condoms, are recommended. 
• Do not breast feed while taking this medication.

Self-Care Tips:

• If given leucovorin tablets take at evenly spaced intervals around-the-clock.
• Drink at least two to three litres of fluid every 24 hours, unless you are instructed otherwise. 
• Get plenty of rest 
• Maintain good nutrition 
• If you experience symptoms or side effects, be sure to discuss them with your doctor.  They can prescribe medications and/or offer other suggestions that are effective in managing such problems.

Monitoring and Testing:

You will be checked regularly by your doctor while you are taking leucovorin, to monitor side effects and check your response to therapy.

How This Drug Works:

Leucovorin is a compound similar to folic acid, which is a necessary vitamin.  It has been around and in use for many decades. Leucovorin is a medication frequently used in combination with the chemotherapy drugs fluoruracil and methotrexate.  Leucovorin is not a chemotherapy drug itself, however it is used in addition to these chemotherapy drugs to enhance anti-cancer effects (with fluorouracil) or to help prevent or lessen side effects (with methotrexate).

Fluorouracil when given alone stays in the body for only a short time.  When given in combination with leucovorin, leucovorin can enhance the binding of fluorouracil to an enzyme inside of the cancer cells. As a result fluorouracil may stay in the cancer cell longer and exert its anti-cancer effect on the cells.  Leucovorin has almost no side effects of its own but when used in combination with fluorouracil it can increase the severity of side effects of that drug.

Methotrexate exerts its chemotherapeutic effect by being able to counteract and compete with folic acid in cancer cells resulting in folic acid deficiency in the cells and causing their death.  This action also effects normal cells which can cause significant side effects in the body, such as: low white, red and platelet blood cell counts, hair loss, mouth sores, difficulty swallowing, diarrhea, liver, lung, nerve and kidney damage.   These complications and side effects of methotrexate can be either prevented or decreased by using leucovorin, which provides a source of folic acid for the body's cells.  Leucovorin is normally started 24 hours after methotrexate is given.  This delay gives the methotrexate a chance to exert its anti-cancer effects.

Leucovorin is also used by itself to treat certain anemia problems when folic acid deficiency is present.

References:

https://www.netdoctor.co.uk/medicines/cancer-drugs/a7998/refolinon-calcium-folinate/

http://chemocare.com/chemotherapy/drug-info/folinic-acid.aspx

https://www.cochrane.org/CD000951/MUSKEL_folic-acid-or-folinic-acid-for-reducing-side-effects-of-methotrexate-for-people-with-rheumatoid-arthritis

https://en.wikipedia.org/wiki/Folinic_acid

https://www.ncbi.nlm.nih.gov/books/NBK545232/