Sulfamethoxazole and Trimethoprim Tablets
»Sulfamethoxazole and Trimethoprim Tablets contain not less than 93.0percent and not more than 107.0percent of the labeled amounts of sulfamethoxazole (C10H11N3O3S)and trimethoprim (C14H18N4O3).
Packaging and storage— Preserve in well-closed,light-resistant containers.
Identification— Transfer an amount of finely ground Tablets,equivalent to 4mg of trimethoprim,to a 10-mLvolumetric flask,add 8mLof methanol,warm for several minutes on a steam bath with frequent shaking,cool,dilute with methanol to volume,mix,and centrifuge briefly.Apply 5µLeach of this solution,a Standard solution of USP Trimethoprim RSin methanol containing 0.4mg per mL,and a Standard solution of USP Sulfamethoxazole RSin methanol containing 2mg per mLto separate points about 3cm from one end of a thin-layer chromatographic plate coated with chromatographic silica gel mixture.Dry the spots in a current of warm air,and develop the plate with a mixture of chloroform,isopropyl alcohol,and diethylamine (6:5:1)in a chamber lined with filter paper.Remove the plate,dry,and examine under short-wavelength UVlight:the trimethoprim and sulfamethoxazole spots from the solution under test have the same RFvalues as the spots from the corresponding Standard solutions.
Dissolution á711ñ—
Medium: 0.1Nhydrochloric acid;900mL.
Apparatus 2: 75rpm.
Time: 60minutes.
Procedure— Determine the amounts of sulfamethoxazole (C10H11N3O3S)and trimethoprim (C14H18N4O3)dissolved,employing the procedure set forth in the Assay,making any necessary volumetric adjustments (see Chromatography á621ñ).Calculate the percentage of each active component dissolved by comparison of the peak responses obtained from a filtered aliquot of the solution under test with the peak responses from the corresponding component obtained from the Standard preparation.
Tolerances— Not less than 70%(Q)of the labeled amounts of C10H11N3O3Sand C14H18N4O3is dissolved in 60minutes.
Uniformity of dosage units á905ñ: meet the requirements.
Assay—
Mobile phase,Standard preparation,and Chromatographic system— Prepare as directed in the Assayunder Sulfamethoxazole and Trimethoprim Oral Suspension.
Assay preparation— Weigh and finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 160mg of sulfamethoxazole,to a 100-mLvolumetric flask.Add about 50mLof methanol and sonicate,with intermittent shaking,for 5minutes.Allow to equilibrate to room temperature,dilute with methanol to volume,mix,and filter.Transfer 5.0mLof the clear filtrate to a 50-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.
Procedure— Separately inject equal volumes (about 20µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantities,in mg,of trimethoprim (C14H18N4O3)and sulfamethoxazole (C10H11N3O3S)in the portion of Tablets taken by the formula:
1000C(rU/rS),
in which Cis the concentration,in mg per mL,of the appropriate USP Reference Standard in the Standard preparation;and rUand rSare the responses of the corresponding analyte obtained from the Assay preparationand the Standard preparation,respectively.
Auxiliary Information— Staff Liaison:Behnam Davani,Ph.D.,MBA,Senior Scientist
Expert Committee:(PA7)Pharmaceutical Analysis 7
USP28–NF23Page 1831
Pharmacopeial Forum:Volume No.29(3)Page 670
Phone Number:1-301-816-8394