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Levoleucovorin

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Levoleucovorin

Levoleucovorin

CLINICAL PHARMACOLOGY

Mechanism Of Action

levoleucovorin is the pharmacologically active isomer of 5-formyl tetrahydrofolic acid. levoleucovorin does not require reduction by the enzyme dihydrofolate reductase in order to participate in reactions utilizing folates as a source of “one-carbon” moieties. Administration of levoleucovorin can counteract the therapeutic and toxic effects of folic acid antagonists such as methotrexate, which act by inhibiting dihydrofolate reductase.

Pharmacodynamics

levoleucovorin is activelyand passivelytransported across cell membranes. In vivo, levoleucovorin is converted to 5-methyltetrahydrofolic acid (5-methyl-THF), the primary circulating form of active reduced folate.levoleucovorin and 5-methyl-THF are polyglutamated intracellularly by the enzyme folylpolyglutamate synthetase.Folylpolyglutamates are active and participate in biochemical pathways that require reduced folate.

Pharmacokinetics

The pharmacokinetics of levoleucovorin after intravenous administration of a 15 mg dose was studied in healthy male volunteers. After rapid intravenous administration, serum total tetrahydrofolate (total-THF) concentrations reached a mean peak of 1722 ng/mL. Serum (6S)-5-methyl-5,6,7,8-tetrahydrofolate concentrations reached a mean peak of 275 ng/mL and the mean time to peak was 0.9 hours. The mean terminal half-life for total-THF and (6S)-5-methyl-5,6,7,8-tetrahydrofolate was 5.1 and 6.8 hours, respectively.

Animal Toxicology And/Or Pharmacology

The acute intravenous LD50 values in adult mice and rats were 575 mg/kg (1725 mg/m²) and 378 mg/kg ( 2268 mg/m²), respectively. Signs of sedation, tremors, reduced motor activity, prostration, labored breathing, and/or convulsion were observed in these studies. Anticipated human dose for each administration is approximately 5 mg/m², which represents a 3-log safety margin.

Clinical Studies

The safety and efficacy of levoleucovorin rescue following high-dose methotrexate were evaluated in 16 patients age 6-21 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 g/m² IV over 4 hours was administered to 13 patients, who received levoleucovorin 7.5 mg every 6 hours for 60 hours or longer beginning 24 hours after completion of methotrexate. Three patients received methotrexate 12.5 g/m² IV over 6 hours, followed by levoleucovorin 7.5 mg 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]

Last reviewed on RxList: 3/31/2008
This monograph has been modified to include the generic and brand name in many instances.

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