Packaging and storage—
Preserve in well-closed containers. A unit-of-use container contains a quantity of Tablets sufficient to provide one week's therapy as indicated in the labeling.
Labeling—
When packaged in a unit-of-use container, the label indicates the total amount of methotrexate present as one week's supply.
Identification—
Dissolve 1 Tablet in 100 mL of dilute hydrochloric acid (1 in 100), and filter the solution: the UV absorption spectrum of the filtrate exhibits maxima and minima at the same wavelengths as that of a solution containing about 2.5 mg of
USP Methotrexate RS in 100 mL of dilute hydrochloric acid (1 in 100).
Dissolution 
711
—
Medium:
0.1 N hydrochloric acid; 900 mL.
Apparatus 2:
50 rpm.
Time:
45 minutes.
Procedure—
Determine the amount of C
20H
22N
8O
5 dissolved from UV absorbances at the wavelength of maximum absorbance at about 306 nm of filtered portions of the solution under test, suitably diluted with
Dissolution Medium, in comparison with a Standard solution having a known concentration of
USP Methotrexate RS in the same
Medium.
Tolerances—
Not less than 75% (Q) of the labeled amount of C20H22N8O5 is dissolved in 45 minutes.
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—
Weigh and finely powder not less than 20 Tablets. Weigh accurately a portion of the powder, equivalent to about 25 mg of methotrexate, and transfer to a 250-mL volumetric flask. Add about 200 mL of Mobile phase, and dissolve the methotrexate using a mechanical shaker or ultrasonic bath. 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 (C
20H
22N
8O
5) in the portion of Tablets taken by the formula:
250C(PU / PS),
in which
C is the concentration, in mg per mL, of
USP Methotrexate RS in the
Standard preparation; and
PU and
PS are the peak responses obtained from the
Assay preparation and the
Standard preparation, respectively.
