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What is methotrexate rescue?
One treatment of osteosarcoma is to administer a high dose of methotrexate, an antimetabolite and folic acid antagonist. Normally, such high doses of methotrexate would be too toxic to administer to a patient because too many healthy cells would be destroyed. The use of FUSILEV rescue therapy after high-dose methotrexate allows protection of the normal tissues with tolerable toxicity.
How does FUSILEV rescue normal tissues and not the tumor?
The rationale for this therapy is based on the mechanism of action of methotrexate, which exerts its biologic activity by binding to an enzyme involved in the activation of folic acid to folinic acid. Administration of folinic acid reverses this inhibition and displaces methotrexate from its binding to the enzyme.
The binding of methotrexate to the enzyme is tighter in cancer cells than in normal cells and therefore the displacement by folinic acid occurs to a lesser degree in cancer cells.
How is FUSILEV used as methotrexate rescue in patients with osteosarcoma?
The doctor will prescribe FUSILEV at the appropriate time(s) to patients receiving methotrexate for osteosarcoma. Patients should contact their physicians or health care practitioners regarding the use of FUSILEV.
How often is FUSILEV given to patients undergoing high-dose methotrexate therapy?
The dosage and frequency of dosing of FUSILEV will depend on the dose of methotrexate and several other factors. Patients should contact their physicians or heathcare practitioners, who will be able to provide specific information and who will make adjustments to dosages as necessary.
How is FUSILEV used in delayed methotrexate elimination?
Dose adjustments may be required if methotrexate is not able to be cleared from the system normally. The doctor will need to have the levels of methotrexate in the body monitored carefully, such as through blood sampling and other types of tests, and will use this information to determine how to best give FUSILEV.
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