» Methotrexate Injection is a sterile solution of Methotrexate in Water for Injection prepared with the aid of Sodium Hydroxide. It contains not less than 90.0 percent and not more than 110.0 percent of the labeled amount of methotrexate (C20H22N8O5).
Packaging and storage Preserve in single-dose or in multiple-dose containers, preferably of Type I glass, protected from light.
USP Reference standards 11
USP Endotoxin RS
Identification Dilute, if necessary, a volume of Injection, equivalent to about 25 mg of methotrexate, with 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 of 0.45-µm pore size. 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.
Other requirements It meets the requirements under Injections 1.
pH 6.0 Buffer solution, Mobile phase, System suitability solution, System suitability test, and Standard preparation Proceed as directed in the Assay under Methotrexate.
Assay preparation Transfer an accurately measured volume of Injection, equivalent to about 25 mg of methotrexate, to a 250-mL volumetric flask, dilute with Mobile phase to volume, and mix.
Procedure Proceed as directed for Procedure in the Assay under Methotrexate. Calculate the quantity, in mg, of methotrexate (C20H22N8O5) in each mL of the Injection taken by the formula:
250(C/V)(PU/PS)in which C is the concentration, in mg per mL, of USP Methotrexate RS in the Standard preparation; V is the volume, in mL, of Injection taken; and PU and PS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.
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USP35NF30 Page 3857