Levoleucovorin

Limitations of Use

Levoleucovorin for Injection is not indicated for pernicious anemia and megaloblastic anemia secondary to the lack of vitamin B₁₂, because of the risk of progression of neurologic manifestations despite hematologic remission.

Levoleucovorin for injection is indicated for intravenous administration only. Do not administer intrathecally.

Due to the risk of precipitation, do not co-administer levoleucovorin for injection with other agents in the same admixture.

The recommended dosage for levoleucovorin for injection is based on a methotrexate dose of 12 grams/m² administered by intravenous infusion over 4 hours. Twenty-four hours after starting the methotrexate infusion, initiate levoleucovorin for injection at a dose of 7.5 mg (approximately 5 mg/m²) as an intravenous infusion every 6 hours.

Monitor serum creatinine and methotrexate levels at least once daily. Continue levoleucovorin for injection administration, hydration, and urinary alkalinization (pH of 7 or greater) until the methotrexate level is below 5 x 10^-8 M (0.05 micromolar). Adjust the levoleucovorin for injection dose or extend the duration as recommended in Table 1.

Start levoleucovorin for injection as soon as possible after an overdosage of methotrexate or within 24 hours of methotrexate administration when methotrexate elimination is impaired. As the time interval between methotrexate administration and levoleucovorin for injection increases, the effectiveness of levoleucovorin for injection to diminish methotrexate toxicity may decrease. Administer levoleucovorin for injection 7.5 mg (approximately 5 mg/m² ) by intravenous infusion every 6 hours until the serum methotrexate level is less than 5 x 10^-8 M (0.05 micromolar).

Monitor serum creatinine and methotrexate levels at least every 24 hours. Increase the dosage of levoleucovorin for injection to 50 mg/m² intravenously every 3 hours and continue levoleucovorin for injection at this dosage until the methotrexate level is less than 5 x 10^-8 M for the following:

• if serum creatinine at 24-hours increases 50% or more compared to baseline
• if the methotrexate level at 24-hours is greater than 5 x 10^-6 M
• if the methotrexate level at 48-hours is greater than 9 x 10^-7 M,

Continue concomitant hydration (3 L per day) and urinary alkalinization with sodium bicarbonate. Adjust the sodium bicarbonate dose to maintain urine pH at 7 or greater.

The following regimens have been used for the treatment of colorectal cancer:

• Levoleucovorin for injection 100 mg/m² by intravenous injection over a minimum of 3 minutes, followed by fluorouracil at 370 mg/m² by intravenous injection, once daily for 5 consecutive days.
• Levoleucovorin for injection 10 mg/m² by intravenous injection, followed by fluorouracil 425 mg/m² by intravenous injection, once daily for 5 consecutive days.

Administer fluorouracil and levoleucovorin for injection separately to avoid the formation of a precipitate.

This five-day course may be repeated every 4 weeks for 2 courses, then every 4 to 5 weeks, if the patient has recovered from the toxicity from the prior course. Do not adjust levoleucovorin for injection dosage for toxicity.

Refer to fluorouracil prescribing information for information on fluorouracil dosage and dosage modifications for adverse reactions.

Because of the calcium content of the levoleucovorin solution, inject no more than 16 mL (160 mg of levoleucovorin) intravenously per minute.

Leucovorin products increase the toxicities of fluorouracil [see Drug Interactions (7)]. Gastrointestinal toxicities, including stomatitis and diarrhea, occur more commonly and may be of greater severity and of prolonged duration. Deaths from severe enterocolitis, diarrhea, and dehydration have occurred in elderly patients receiving weekly d,l-leucovorin and fluorouracil.

Monitor patients for gastrointestinal toxicities. Do not initiate or continue therapy with levoleucovorin and fluorouracil in patients with symptoms of gastrointestinal toxicity until those symptoms have resolved. Monitor patients with diarrhea until resolved, as rapid deterioration leading to death can occur.

The concomitant use of d,l-leucovorin with trimethoprim-sulfamethoxazole for the acute treatment of Pneumocystis jiroveci pneumonia in patients with HIV infection was associated with increased rates of treatment failure and morbidity [see Drug Interactions (7)].

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

The following adverse reaction have been identified during postapproval use of levoleucovorin products. Because these reactions are reported from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

Dermatologic: pruritus, rash

Respiratory: dyspnea

Other: temperature change, rigors, allergic reactions

The safety and effectiveness of levoleucovorin have been established in pediatric patients for rescue after high-dose methotrexate therapy in osteosarcoma and diminishing the toxicity associated with overdosage of folic acid antagonists or impaired methotrexate elimination. Use of levoleucovorin in pediatric patients is supported by open-label clinical trial data in 16 pediatric patients 6 years of age and older, with additional supporting evidence from literature [see Clinical Studies (14.1)].

The safety and effectiveness of levoleucovorin have not been established for the treatment of pediatric patients with advanced metastatic colorectal cancer.

Clinical studies of levoleucovorin in the treatment of osteosarcoma did not include patients aged 65 and over to determine whether they respond differently from younger patients.

In the NCCTG clinical trial of levoleucovorin in combination with fluorouracil for the treatment of metastatic colorectal cancer, no overall differences in safety or effectiveness were observed between patients age 65 years and older and younger patients.

The pharmacokinetics of levoleucovorin after intravenous administration of a 15 mg dose was studied in healthy subjects. The mean maximum serum total tetrahydrofolate (total-THF) concentrations was 1722 ng/mL (CV 39%) and the mean maximum serum (6S)-5-methyl-5,6,7,8-tetrahydrofolate concentrations was 275 ng/mL (CV 18%) observed around 0.9 hours post injection.

No studies have been conducted to evaluate the potential of levoleucovorin for carcinogenesis, mutagenesis and impairment of fertility.

The efficacy of levoleucovorin rescue following high-dose methotrexate was evaluated in 16 patients aged 6 to 21 years who received 58 courses of therapy for osteogenic sarcoma. High-dose methotrexate was one component of several different combination chemotherapy regimens evaluated across several trials. Methotrexate 12 grams/m² as an intravenous infusion over 4 hours was administered to 13 patients, who received levoleucovorin 7.5 mg by intravenous infusion every 6 hours for 60 hours or longer beginning 24 hours after completion of methotrexate. Three patients received methotrexate 12.5 grams/m² intravenously over 6 hours, followed by levoleucovorin 7.5 mg by intravenous infusion every 3 hours for 18 doses beginning 12 hours after completion of methotrexate. The mean number of levoleucovorin doses per course was 18.2 and the mean total dose per course was 350 mg. The efficacy of levoleucovorin rescue following high-dose methotrexate was based on the adverse reaction profile [see Adverse Reactions (6.1)].

In a randomized clinical study conducted by Mayo Clinic and the North Central Cancer Treatment Group (NCCTG) in patients with metastatic colorectal cancer comparing d,l-leucovorin 200 mg/m² and fluorouracil 370 mg/m² versus d,l-leucovorin 20 mg/m² and fluorouracil 425 mg/m² versus fluorouracil 500 mg/m², with all drugs administered by intravenous infusion daily for 5 days every 28 to 35 days, response rates were 26% (p=0.04 versus fluorouracil alone), 43% (p=0.001 versus fluorouracil alone) and 10%, respectively. Respective median survival times were 12.2 months (p=0.037), 12 months (p=0.050), and 7.7 months. The low dose d,l-leucovorin regimen was associated with a statistically significant improvement in weight gain of more than 5%, relief of symptoms, and improvement in performance status. The high dose d,l-leucovorin regimen was associated with a statistically significant improvement in performance status and trended toward improvement in weight gain and in relief of symptoms but these were not statistically significant.

In a second randomized clinical study conducted by Mayo Clinic and NCCTG, the fluorouracil alone arm was replaced by a regimen of sequentially administered methotrexate, fluorouracil, and d,l-leucovorin. Response rates with d,l-leucovorin 200 mg/m² and fluorouracil 370 mg/m² versus d,l-leucovorin 20 mg/m² and fluorouracil 425 mg/m² versus sequential methotrexate and fluorouracil and d,l-leucovorin were respectively 31% (p≤0.01), 42% (p≤0.01), and 14%. Respective median survival times were 12.7 months (p≤0.04), 12.7 months (p≤0.01), and 8.4 months. There was no statistically significant difference in weight gain of more than 5% or in improvement in performance status was seen between the treatment arms.

A randomized controlled trial conducted by NCCTG in patients with metastatic colorectal cancer failed to show superiority of a regimen of fluorouracil + levoleucovorin to fluorouracil + d,l-leucovorin in overall survival. Patients were randomized to fluorouracil 370 mg/m² intravenously and levoleucovorin 100 mg/m² intravenously, both daily for 5 days, or to fluorouracil 370 mg/m² intravenously and d,l-leucovorin 200 mg/m² intravenously, both daily for 5 days. Treatment was repeated week 4 and week 8, and then every 5 weeks until disease progression or unacceptable toxicity.