Thioguanine Tablets

» Thioguanine Tablets contain not less than 93.0 percent and not more than 107.0 percent of the labeled amount of C5H5N5S.

Packaging and storage— Preserve in tight containers.

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USP Thioguanine RS

Identification— The UV absorption spectrum of the Acidic assay preparation employed for measurement of absorbance in the Assay exhibits maxima and minima at the same wavelengths as that of a similar solution of USP Thioguanine RS, concomitantly measured.

Dissolution

711

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Medium: water; 900 mL.

Apparatus 2: 50 rpm.

Time: 45 minutes.

Standard preparation— Dissolve an accurately weighed quantity of USP Thioguanine RS in 1 N sodium hydroxide to obtain a solution having a known concentration of about 4.5 µg per mL.

Procedure— Determine the amount of C5H5N5S dissolved from UV absorbances at the wavelength of maximum absorbance at about 348 nm of filtered portions of the solution under test, suitably diluted with 0.1 N hydrochloric acid, in comparison with the Standard preparation.

Tolerances— Not less than 75% (Q) of the labeled amount of C5H5N5S is dissolved in 45 minutes.

Uniformity of dosage units

905

: meet the requirements.

Assay—

Standard preparations— Dissolve an accurately weighed quantity of USP Thioguanine RS in sodium hydroxide solution (1 in 250), and dilute quantitatively and stepwise with the sodium hydroxide solution to obtain a Standard preparation having a known concentration of 80 µg per mL. Transfer 5.0 mL of this solution to a 100-mL volumetric flask, add dilute hydrochloric acid (1 in 10) to volume, and mix, to obtain the Acidic standard preparation. Transfer another 5.0-mL portion of the solution to a second 100-mL volumetric flask, add 10.0 mL of 1 N sodium hydroxide, dilute with water to volume, and mix, to obtain the Basic standard preparation.

Assay preparations— Weigh and finely powder not less than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 40 mg of thioguanine, to a 500-mL volumetric flask, add 50 mL of 1 N sodium hydroxide, and allow to stand for 10 minutes, with frequent swirling. Dilute with water to volume, mix, and filter a portion of the solution through a pledget of glass wool. Transfer 5.0 mL of the filtrate to a 100-mL volumetric flask, add dilute hydrochloric acid (1 in 10) to volume, and mix, to obtain the Acidic assay preparation. Transfer another 5.0-mL portion of the filtrate to a second 100-mL volumetric flask, add 10.0 mL of 1 N sodium hydroxide, dilute with water to volume, and mix, to obtain the Basic assay preparation.

Procedure— Concomitantly determine the absorbances of the Acidic assay preparation and the Acidic standard preparation in 1-cm cells at the wavelength of maximum absorbance at about 348 nm, with a suitable spectrophotometer, using the Basic assay preparation and the Basic standard preparation, respectively, as the blanks. Calculate the quantity, in mg, of C5H5N5S in the portion of Tablets taken by the formula:

10C(AU / AS)

in which C is the concentration, in µg per mL, of USP Thioguanine RS in the Acidic standard preparation, and AU and AS are the absorbances of the Acidic assay preparation and the Acidic standard preparation, respectively.

Auxiliary Information— Please check for your question in the FAQs before contacting USP.

Topic/Question	Contact	Expert Committee
Monograph	Feiwen Mao, M.S. Senior Scientific Liaison 1-301-816-8320	(SM32010) Monographs - Small Molecules 3
Reference Standards	RS Technical Services 1-301-816-8129 rstech@usp.org
711	Margareth R.C. Marques, Ph.D. Senior Scientific Liaison 1-301-816-8106	(GCDF2010) General Chapters - Dosage Forms

USP35–NF30 Page 4845