Packaging and storage—
Preserve in well-closed containers.Aunit-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 1Tablet in 100mLof dilute hydrochloric acid (1in 100),and filter the solution:the UVabsorption spectrum of the filtrate exhibits maxima and minima at the same wavelengths as that of a solution containing about 2.5mg of
USP Methotrexate RSin 100mLof dilute hydrochloric acid (1in 100).
Dissolution á711ñ—
Medium:
0.1Nhydrochloric acid;900mL.
Apparatus 2:
50rpm.
Time:
45minutes.
Procedure—
Determine the amount of C
20H
22N
8O
5dissolved from UVabsorbances at the wavelength of maximum absorbance at about 306nm 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 RSin the same
Medium.
Tolerances—
Not less than 75%(Q)of the labeled amount of C20H22N8O5is dissolved in 45minutes.
Assay—
pH6.0Buffer solution
,
Mobile phase,
System suitability preparation,
System suitability test,and
Standard preparation—Proceed as directed in the
Assayunder
Methotrexate.
Assay preparation—
Weigh and finely powder not less than 20Tablets.Weigh accurately a portion of the powder,equivalent to about 25mg of methotrexate,and transfer to a 250-mLvolumetric flask.Add about 200mLof Mobile phase,and dissolve the methotrexate using a mechanical shaker or ultrasonic bath.Dilute with Mobile phaseto volume,and mix.
Procedure—
Proceed as directed for
Procedurein the
Assayunder
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
Cis the concentration,in mg per mL,of
USP Methotrexate RSin the
Standard preparation;and
PUand
PSare the peak responses obtained from the
Assay preparationand the
Standard preparation,respectively.