Leucovorin Calcium 50mg Injection (Calcium Leucovorin)

Leucovorin Calcium 50mg Injection includes calcium leucovorin (also known as folinic acid), which is an active form of folate. It is not a traditional chemotherapy medicine. Calcium leucovorin can be applied in the protection of normal cells after high-dose methotrexate administration, in managing toxicity or overdose associated with some anti-folate agents, and as a drug that increases the efficacy of 5-fluorouracil (5-FU) in some cases of colorectal and gastrointestinal tumors. The dose and frequency of administration differ depending on the indicated use; the delayed administration of calcium leucovorin in the case of methotrexate rescue may be dangerous.

Uses of Leucovorin Calcium 50mg Injection include:

• High-dose methotrexate therapy rescue
  
• Overdose of methotrexate or delayed clearance of methotrexate
  
• Cancers of the colon and other gastrointestinal regions when administered alongside 5-FU
  
• Specific side effects of folate antagonists
• Folate-deficient megaloblastic anemia where oral administration is unsuitable

In the case of methotrexate rescue, the dosage and schedule depend on the levels of methotrexate in the blood and the duration since the drug was administered. For use alongside 5-FU, calcium leucovorin assists in increasing the effectiveness of the drug against cancer. However, Leucovorin Calcium 50mg Injection is not to be used in treating vitamin B12 deficiency.

There are two primary mechanisms of action for leucovorin calcium 50mg. The first one is with methotrexate, where calcium leucovorin supplies the active form of folate that the normal cells require, hence protecting the cells from the effects of methotrexate. The second one is with 5-FU, where medicine enhances the binding affinity of 5-FU to an enzyme.

High-dose methotrexate rescue: Calcium leucovorin rescue protects normal cells from being harmed by methotrexate, thus making the use of high-dose methotrexate possible.

5-FU/leucovorin evidence: Research has proven that the combination of leucovorin calcium 50mg and 5-FU enhances the impact of 5-FU treatment. This method is applied in FOLFOX and FOLFIRI protocols.​

The medicine has good tolerance among most people, but some may develop adverse reactions due to capsule treatment. Side effects will depend on its application, either in methotrexate rescue, 5-FU, or for some other condition.

Common / expected side effects

• Injection-site discomfort
  
• Nausea/GI upset
  
• Mild rash/itching (uncommon)

Serious side effects requiring prompt medical attention

• Severe hypersensitivity
  
• Increased 5-FU diarrhea/mucositis
  
• Seizure worsening via antiepileptic interactions
• Fatal toxicity with intrathecal administration
  

Important: These are only general references to be used when giving treatments. The physician will prescribe the proper dosage, frequency, interaction with other drugs, adjustment of dosage because of renal or hepatic dysfunction, and management of adverse effects depending on the patient's status.

For methotrexate rescue, a delayed or missed dose is potentially urgent. Contact the oncology team immediately rather than waiting for the next scheduled dose.

• Serum methotrexate concentrations will be measured to ensure that the drug is being properly excreted from the body and to determine the leucovorin calcium 50mg dose.
  
• The function of the kidneys and the amount of urine produced will be observed because the kidneys play a role in excreting methotrexate from the body.
  
• Blood work, mouth ulcers, and diarrhea could be measured when the drugs Calcium leucovorin and 5-FU are used together.
  
• Hydration and electrolyte measurements are performed to maintain fluid and electrolyte balance.
  

• Current leucovorin calcium injection prescribing information https://www.accessdata.fda.gov/drugsatfda_docs/label/2012/040347s010lbl.pdf​
  
• Current high-dose methotrexate rescue protocols https://pmc.ncbi.nlm.nih.gov/articles/PMC11903593/​
  
• Evidence supporting 5-FU/leucovorin colorectal regimens https://www.sciencedirect.com/science/article/pii/S0923753419478290​
  
• Current NCCN colorectal-cancer guidelines https://www.nccn.org/patients/guidelines/content/PDF/colon-patient.pdf​​