U.S. PHARMACOPEIA

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Methotrexate for Injection
» Methotrexate for Injection is a sterile, freeze-dried preparation of methotrexate sodium with or without suitable added substances, buffers, and/or diluents. It contains not less than 95.0 percent and not more than 115.0 percent of the labeled amount of methotrexate (C20H22N8O5).
Caution—Great care should be taken to prevent inhaling particles of methotrexate sodium and exposing the skin to it.
Packaging and storage— Preserve in Containers for Sterile Solids as described under Injections 1, protected from light.
Constituted solution— At the time of use, it meets the requirements for Constituted Solutions under Injections 1.
Identification— Dissolve a sufficient quantity in water to obtain a solution having a concentration of about 2.5 mg per mL. Adjust with 0.1 N hydrochloric acid to a pH of 4.0. Place the slurry in a 50-mL centrifuge tube, and centrifuge. Decant the supernatant, add 25 mL of acetone, shake, and filter through a solvent-resistant, membrane filter having a porosity of 0.45 µm. Air-dry the filtered precipitate: the methotrexate so obtained responds to Identification test A under Methotrexate.
Bacterial endotoxins 85— It contains not more than 0.4 USP Endotoxin Unit per mg of methotrexate sodium.
pH 791: between 7.0 and 9.0 in a solution constituted as directed in the labeling, except that water is used as the diluent.
Residual solvents 467: meets the requirements.
(Official January 1, 2007)
Other requirements— It meets the requirements for Labeling under Injections 1, for Sterility Tests 71, and for Uniformity of Dosage Units 905.
Assay—
pH 6.0 Buffer solution , Mobile phase, System suitability preparation, System suitability test, and Standard preparation—Proceed as directed in the Assay under Methotrexate.
Assay preparation— Dissolve the contents of 1 container of Methotrexate for Injection in an accurately measured volume of Mobile phase to obtain a solution having a known concentration of about 0.1 mg per mL.
Procedure— Proceed as directed for Procedure in the Assay under Methotrexate. Calculate the quantity, in mg, of methotrexate (C20H22N8O5) in the container of Methotrexate for Injection taken by the formula:
C(L/D)(rU/rS),
in which C is the concentration, in mg per mL, of USP Methotrexate RS, corrected for water content, in the Standard preparation; L is the labeled quantity of Methotrexate in the container; D is the concentration, in mg per mL, of Methotrexate in the Assay preparation on the basis of the labeled quantity in the container and the extent of dilution; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.
Auxiliary Information— Staff Liaison : Feiwen Mao, M.S., Senior Scientific Associate
Expert Committee : (MDOOD05) Monograph Development-Ophthalmics Oncologics and Dermatologicals
USP29–NF24 Page 1384
Phone Number : 1-301-816-8320