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Dosage of levoleucovorin is highly individualized and depends entirely on the clinical indication and the dose of the primary chemotherapy agent being used.

• Methotrexate Rescue (Osteosarcoma): The standard dose is often 7.5 mg administered intravenously every 6 hours. This typically begins 24 hours after the start of the methotrexate infusion. The duration of 'rescue' continues until methotrexate blood levels fall below a specific threshold (usually <0.05 micromolar).
• Methotrexate Overdose: If an overdose occurs, levoleucovorin should be administered as soon as possible. A common starting dose is 75 mg IV, followed by 7.5 mg IV every 6 hours until methotrexate levels are safe.
• Colorectal Cancer (with 5-FU): Two common regimens exist. One involves 100 mg/m² of levoleucovorin administered by slow IV injection over at least 3 minutes, followed by 5-FU. Another regimen involves 10 mg/m² administered daily for five days, repeated at 4-week intervals.

Levoleucovorin is approved for use in pediatric patients for the rescue of high-dose methotrexate toxicity in osteosarcoma.

• Dosing: Pediatric dosing is generally based on body surface area (BSA). The typical dose is 7.5 mg/m² every 6 hours, starting 24 hours after methotrexate.
• Monitoring: Close monitoring of serum creatinine and methotrexate levels is even more critical in children to prevent permanent renal damage.

Renal Impairment

Patients with kidney dysfunction are at a significantly higher risk of methotrexate toxicity because methotrexate is cleared by the kidneys. While levoleucovorin itself does not usually require a dose reduction for renal impairment, the duration and frequency of administration must be increased if the patient's creatinine clearance is low or if methotrexate levels remain high.

Hepatic Impairment

There are no specific dose adjustment guidelines for patients with liver disease. However, because levoleucovorin is converted to its active metabolite in the liver, healthcare providers may monitor these patients more closely for efficacy and side effects.

Elderly Patients

Clinical studies did not include sufficient numbers of subjects aged 65 and over to determine if they respond differently than younger subjects. In general, dose selection for an elderly patient should be cautious, reflecting the greater frequency of decreased hepatic, renal, or cardiac function.

• Administration: Levoleucovorin is almost always administered in a clinical setting by a nurse or doctor. It is given as an intravenous (IV) infusion or an intramuscular (IM) injection.
• Rate of Infusion: For colorectal cancer regimens, the infusion should not exceed 160 mg per minute due to the calcium content of the solution.
• Compatibility: It should not be mixed in the same IV bag as 5-fluorouracil, as a precipitate may form. They must be administered sequentially.
• Storage: Unopened vials should be stored in a refrigerator (2°C to 8°C or 36°F to 46°F) and protected from light.

In the context of chemotherapy rescue, a missed dose is a medical emergency. If a dose is missed, it must be administered as soon as possible. Delayed administration can lead to severe, irreversible methotrexate toxicity, including bone marrow suppression and organ failure. Patients should contact their oncology team immediately if a scheduled infusion is delayed.

An overdose of levoleucovorin itself is generally not considered life-threatening, as it is a water-soluble vitamin derivative. However, excessively high doses may interfere with the chemotherapeutic effect of methotrexate (making the cancer treatment less effective).

• Symptoms: There are no specific symptoms of levoleucovorin overdose.
• Management: Treatment is supportive. If an overdose occurs, healthcare providers will monitor for any signs of reduced chemotherapy efficacy.

> Important: Follow your healthcare provider's dosing instructions. Do not adjust your dose without medical guidance. The timing of levoleucovorin in relation to methotrexate is critical for safety.

Because levoleucovorin is almost always administered with potent chemotherapy agents like 5-fluorouracil or methotrexate, it is often difficult to distinguish which side effects are caused by levoleucovorin and which are caused by the chemotherapy. However, when used with 5-FU, the following are frequently reported:

• Diarrhea: This is the most common side effect. It can range from mild to severe (life-threatening). It typically occurs within a few days of treatment.
• Nausea and Vomiting: Patients often experience significant gastrointestinal upset. This is usually managed with anti-emetic (anti-nausea) medications.
• Stomatitis (Mouth Sores): Inflammation and ulcers in the mouth and throat can make eating and drinking painful. This usually develops 5-10 days after treatment starts.
• Fatigue: A general feeling of tiredness or lack of energy is very common during treatment cycles.
• Anorexia: Loss of appetite is frequent, often secondary to nausea or mouth sores.

• Leukopenia: A decrease in white blood cell counts, which increases the risk of infection. This is primarily driven by the 5-FU but can be exacerbated by the metabolic shifts caused by levoleucovorin.
• Alopecia: Thinning of the hair or hair loss.
• Dermatitis: Skin rashes or dry, itchy skin.
• Taste Perversion: A metallic or unusual taste in the mouth.

• Seizures: There have been rare reports of seizures in patients receiving levoleucovorin, particularly in those with pre-existing CNS conditions or those receiving high doses.
• Syncope: Fainting or temporary loss of consciousness.
• Thrombocytosis: An abnormal increase in the number of platelets in the blood.

> Warning: Stop taking Levoleucovorin and call your doctor immediately if you experience any of these.

• Anaphylaxis / Severe Allergic Reaction: Symptoms include hives, itching, swelling of the face, lips, or tongue, and difficulty breathing. This is a medical emergency.
• Severe Enterocolitis: Severe abdominal pain combined with watery or bloody diarrhea and fever. This can lead to bowel perforation.
• Severe Dehydration: Signs include extreme thirst, dark urine, dizziness, and confusion, often resulting from uncontrolled vomiting or diarrhea.
• Neurological Changes: Sudden confusion, seizures, or loss of coordination.

Levoleucovorin is typically used in cycles rather than as a continuous long-term medication. Therefore, long-term cumulative side effects are rare. However, repeated cycles can lead to:

• Chronic Nutritional Deficiencies: If stomatitis and diarrhea are not well-managed, patients may suffer from long-term weight loss and vitamin imbalances.
• Peripheral Neuropathy: While more commonly associated with other chemotherapy agents (like oxaliplatin) often given alongside levoleucovorin, persistent tingling or numbness in hands and feet can occur.

No FDA black box warnings for Levoleucovorin. However, it is vital to note that levoleucovorin significantly increases the toxicity of 5-fluorouracil. While it makes 5-FU more effective at killing cancer, it also makes it more toxic to the gut and bone marrow. Deaths from severe enterocolitis and myelosuppression have been reported when these drugs are used in combination, particularly in elderly or debilitated patients.

Report any unusual symptoms to your healthcare provider. Early intervention is key to managing the side effects of combination chemotherapy.

Levoleucovorin is a potent metabolic agent. Its primary danger lies not in its own toxicity, but in how it interacts with chemotherapy and how it can mask other medical conditions. It must only be administered under the supervision of an experienced oncologist.

No FDA black box warnings for Levoleucovorin.

• Allergic Reactions: There is a risk of hypersensitivity and anaphylactoid reactions. Patients with a known allergy to leucovorin (the racemic mixture) must not receive levoleucovorin, as they will likely react to the l-isomer as well.
• Intrathecal Administration Warning: Levoleucovorin must NEVER be administered intrathecally (into the spinal canal). This can be fatal. It is for intravenous or intramuscular use only.
• Enhancement of 5-FU Toxicity: When used with 5-fluorouracil, levoleucovorin increases the risk of severe gastrointestinal toxicity. Patients who develop diarrhea must be monitored extremely closely until the diarrhea resolves, as rapid clinical deterioration can occur.
• Seizure Risk: Use with caution in patients with a history of epilepsy or seizures. Levoleucovorin may increase the frequency of seizures in susceptible individuals, possibly by reducing the blood levels of anti-seizure medications like phenytoin.
• Anemia Masking: Levoleucovorin can improve the blood counts in patients with Vitamin B12 deficiency (pernicious anemia) while allowing the neurological damage caused by the deficiency to progress. It should not be used to treat B12 deficiency.

Patients receiving levoleucovorin require rigorous laboratory monitoring:

• Methotrexate Levels: During rescue therapy, serum methotrexate levels must be checked every 12 to 24 hours to determine when it is safe to stop levoleucovorin.
• Renal Function: Serum creatinine must be checked daily during high-dose methotrexate therapy. Any rise in creatinine suggests delayed methotrexate clearance and requires an immediate increase in levoleucovorin dosage.
• Complete Blood Count (CBC): To monitor for white blood cell and platelet drops, especially when used with 5-FU.
• Electrolytes: To monitor for imbalances caused by diarrhea or vomiting.

Levoleucovorin itself does not typically cause drowsiness or cognitive impairment. However, the chemotherapy agents it is paired with, as well as the anti-nausea medications used alongside it, may cause significant fatigue or dizziness. Patients should assess their reaction to the entire treatment regimen before driving.

There is no direct interaction between alcohol and levoleucovorin. However, alcohol can irritate the lining of the mouth and gut, worsening the stomatitis and diarrhea caused by chemotherapy. It can also strain the liver, which is processing the chemotherapy drugs. Healthcare providers generally recommend avoiding alcohol during active treatment.

In the context of methotrexate rescue, levoleucovorin must not be discontinued until methotrexate levels are confirmed to be below the safety threshold. Stopping too early can result in severe, delayed toxicity. There is no withdrawal syndrome associated with levoleucovorin.

> Important: Discuss all your medical conditions with your healthcare provider before starting Levoleucovorin.

• Intrathecal Methotrexate: While levoleucovorin is used for systemic methotrexate, it should not be given alongside intrathecal methotrexate (methotrexate injected into the spine), as it may interfere with the effectiveness of the treatment in the CNS.
• Pernicious Anemia Treatment: Levoleucovorin should not be used as a standalone treatment for Vitamin B12 deficiency, as it can mask the hematologic symptoms while allowing permanent neurological damage to occur.

• 5-Fluorouracil (5-FU): This is a therapeutic interaction, but it is also a dangerous one. Levoleucovorin increases the binding of 5-FU to its target enzyme, which significantly increases both the efficacy and the toxicity (especially diarrhea and mouth sores). Dosage of 5-FU may need to be reduced.
• Phenytoin (Dilantin): Levoleucovorin may increase the metabolism of phenytoin in the liver, leading to lower levels of the anticonvulsant in the blood. This can increase the risk of seizures. Patients may need their phenytoin dose adjusted.
• Phenobarbital and Primidone: Similar to phenytoin, levoleucovorin can decrease the plasma concentrations of these anti-seizure medications, potentially leading to breakthrough seizures.

• Trimethoprim / Sulfamethoxazole (Bactrim): These antibiotics are also folate antagonists. Using them with levoleucovorin may interfere with the 'rescue' effect or alter the antibiotic's efficacy.
• Capecitabine (Xeloda): Since capecitabine is a prodrug of 5-FU, levoleucovorin will similarly increase its toxicity and efficacy.

Because levoleucovorin is typically administered intravenously in a hospital or clinic setting, food interactions are less of a concern than with oral medications. However:

• Folic Acid Supplements: Taking high-dose over-the-counter folic acid supplements can interfere with the precise dosing of levoleucovorin and the chemotherapy it is meant to modulate. Patients should avoid all vitamin supplements unless approved by their oncologist.
• Green Tea: Some studies suggest green tea may have mild antifolate properties, though this is unlikely to be clinically significant during IV levoleucovorin therapy.

• St. John's Wort: May induce enzymes that could theoretically affect the metabolism of the chemotherapy drugs used with levoleucovorin.
• Antioxidants (Vitamin C, Vitamin E): There is ongoing debate in oncology about whether high-dose antioxidants interfere with the oxidative damage chemotherapy uses to kill cancer cells. Patients should consult their doctor before using these.

• Methotrexate Assays: Levoleucovorin does not usually interfere with standard methotrexate lab tests, but high concentrations of folates in the blood can occasionally cause slight interference with certain older immunoassays.
• B12 Levels: As mentioned, levoleucovorin can normalize blood counts, making it appear that a B12 deficiency has been resolved when it has not.

> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking. Even 'natural' products can interfere with complex chemotherapy protocols.

• Hypersensitivity: Levoleucovorin is strictly contraindicated in patients who have had a previous severe allergic reaction (anaphylaxis) to levoleucovorin, leucovorin, or any component of the formulation. Because levoleucovorin is a component of racemic leucovorin, a reaction to one implies a reaction to the other.
• Pernicious Anemia: It is contraindicated for the treatment of pernicious anemia and other megaloblastic anemias resulting from Vitamin B12 deficiency. Using folate alone in these patients is considered improper medical practice because it fails to treat the underlying B12 deficiency, leading to irreversible subacute combined degeneration of the spinal cord.

• Severe Dehydration or Electrolyte Imbalance: Patients with severe pre-existing diarrhea or vomiting should be stabilized before receiving levoleucovorin/5-FU combinations, as the drug will likely worsen these conditions.
• Active Seizure Disorders: Because levoleucovorin can lower the seizure threshold or reduce the efficacy of anticonvulsants, its use in patients with uncontrolled epilepsy requires a careful risk-benefit analysis and frequent monitoring of anti-seizure drug levels.
• Severe Renal Impairment: While not an absolute contraindication, the presence of kidney failure makes the use of levoleucovorin (in the context of methotrexate rescue) much more complex and dangerous, requiring specialized inpatient care.

Patients who are sensitive to other folic acid derivatives may theoretically be at higher risk for a reaction to levoleucovorin. There is no known cross-sensitivity between levoleucovorin and non-folate related drugs, but all patients should be monitored for the first few minutes of their first infusion for any signs of an infusion reaction.

> Important: Your healthcare provider will evaluate your complete medical history before prescribing Levoleucovorin. Ensure you disclose all previous allergic reactions to medications.

• Risk Summary: Levoleucovorin is classified under the older FDA Pregnancy Category C. There are no adequate and well-controlled studies in pregnant women. It is not known whether levoleucovorin can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity.
• Clinical Considerations: However, levoleucovorin is almost always used with methotrexate or 5-fluorouracil. Methotrexate is a known teratogen (causes birth defects) and is contraindicated in pregnancy. 5-FU also carries significant fetal risks. Therefore, the treatment regimen as a whole is generally avoided during pregnancy unless the mother's life is at stake.
• Fertility: It is unknown if levoleucovorin affects fertility, though the associated chemotherapy often does.

• Excretion in Milk: It is not known whether levoleucovorin is excreted in human milk. Because many drugs are excreted in human milk and because of the potential for serious adverse reactions in nursing infants from the chemotherapy drugs used with levoleucovorin, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.

• Approved Indications: Levoleucovorin is approved for use in children for the rescue of high-dose methotrexate toxicity in the treatment of osteosarcoma.
• Safety Profile: The safety and effectiveness in children for the treatment of colorectal cancer have not been established, as this cancer is extremely rare in pediatric populations.
• Growth Effects: There are no known long-term effects of levoleucovorin on growth and development, though the primary chemotherapy (methotrexate) can have significant impacts.

• Increased Risk: Elderly patients (65 years and older) are at a significantly higher risk of severe gastrointestinal toxicity when levoleucovorin is used with 5-fluorouracil.
• Renal Function: Because older patients are more likely to have decreased renal function, and levoleucovorin's role in methotrexate rescue depends on renal clearance of methotrexate, these patients require very close monitoring of their kidney labs (creatinine and GFR).
• Polypharmacy: Elderly patients are more likely to be taking medications like phenytoin, which interacts with levoleucovorin.

• Methotrexate Context: In patients with renal impairment, methotrexate clearance is delayed. This necessitates higher and more frequent doses of levoleucovorin to prevent systemic toxicity.
• Dialysis: Levoleucovorin and its metabolites are likely dialyzable, though this is rarely used as a primary clearance method compared to ensuring adequate hydration and urinary alkalinization.

• Metabolism: Since the conversion of levoleucovorin to its active metabolite (5-methyltetrahydrofolate) occurs in the liver, patients with severe hepatic impairment (Child-Pugh Class C) might theoretically have altered pharmacokinetics. However, no specific dose adjustments are currently mandated in clinical guidelines.

> Important: Special populations require individualized medical assessment and often require more frequent laboratory monitoring.

Levoleucovorin is the pharmacologically active l-isomer of 5-formyltetrahydrofolate. At the molecular level, it serves as a source of reduced folates.

1. 1Methotrexate Rescue: Methotrexate inhibits the enzyme dihydrofolate reductase (DHFR). Levoleucovorin does not require DHFR for its activity; it is converted to 5,10-methylenetetrahydrofolate and then to 5-methyltetrahydrofolate, providing the necessary folate pool for the synthesis of purines and thymidylate, which are essential for DNA replication.
2. 25-FU Potentiation: 5-fluorouracil inhibits thymidylate synthase (TS). Levoleucovorin is converted into 5,10-methylenetetrahydrofolate, which binds to TS and the 5-FU metabolite (FdUMP). This stabilizes the inhibitory complex, preventing the enzyme from functioning and thereby shutting down DNA synthesis in the tumor.

• Dose-Response: The 'rescue' effect is dose-dependent. If methotrexate levels are very high, levoleucovorin doses must be increased to compete for transport into the cells.
• Onset of Action: When given IV, the onset is nearly immediate.
• Duration: The effects on the folate pool persist for several hours, which is why dosing every 6 hours is standard during rescue protocols.

| Parameter | Value |

|---|---|

| Bioavailability | 100% (IV/IM) |

| Protein Binding | ~27% |

| Half-life | 5.1 to 6.8 hours |

| Tmax | 0.9 hours (IM); End of infusion (IV) |

| Metabolism | Hepatic to 5-methyltetrahydrofolate |

| Excretion | Renal (80-90%), Fecal (5-8%) |

• Molecular Formula: C20H21CaN7O7 (as Calcium salt)
• Molecular Weight: 511.5 g/mol
• Solubility: Sparingly soluble in water; practically insoluble in alcohol.
• Structure: A derivative of folic acid with a formyl group at the 5-position of the pteridine ring.

Levoleucovorin is classified as a Folic Acid Analog and a Cytoprotective Agent. It is related to racemic leucovorin but is more potent by weight because it contains only the active isomer. It is distinct from 'folic acid' (Vitamin B9) because it is already in a reduced, metabolically active state.