Sulfamethoxazole and Trimethoprim Oral Suspension
»Sulfamethoxazole and Trimethoprim Oral Suspension contains not less than 90.0percent and not more than 110.0percent of the labeled amounts of sulfamethoxazole (C10H11N3O3S)and trimethoprim (C14H18N4O3).
Packaging and storage— Preserve in tight,light-resistant containers.
Identification— In the Chromatographic puritytest,the respective Test solutionsexhibit spots whose RFvalues correspond to those spots produced by the Standard solutionsof USP Trimethoprim RSand USP Sulfamethoxazole RS.
Uniformity of dosage units á905ñ—
FOR ORAL SUSPENSION PACKAGED IN SINGLE-UNIT CONTAINERS: meets the requirements.
Deliverable volume á698ñ—
FOR ORAL SUSPENSION PACKAGED IN MULTIPLE-UNIT CONTAINERS: meets the requirements.
pHá791ñ: between 5.0and 6.5.
Chromatographic purity—
LIMIT OF TRIMETHOPRIM DEGRADATION PRODUCT—
Test solution— Transfer an accurately measured volume of Oral Suspension,equivalent to about 40mg of trimethoprim,to a separatory funnel.Extract with three 25-mLportions of a mixture of chloroform and methanol (8:2),collecting the extracts in a 125-mLconical flask.Evaporate the combined extracts with the aid of a current of air to dryness on a steam bath.Dissolve the residue in 2.0mLof the mixture of chloroform and methanol (8:2),then centrifuge.
Standard solution A— Dissolve an accurately weighed quantity of USP Trimethoprim RSin a mixture of chloroform and methanol (8:2)to obtain a solution having a known concentration of about 20mg per mL.
Standard solution B— Dilute an accurately measured volume of Standard solution Awith a mixture of chloroform and methanol (8:2)to obtain a solution having a known concentration of about 0.1mg per mL.
Procedure— Apply 5µLeach of the Test solution,Standard solution A,and Standard solution Bto separate points on a thin-layer chromatographic plate (see Chromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel.Place the plate in a saturated chromatographic chamber,and develop the chromatogram in a solvent system consisting of a mixture of chloroform,methanol,and ammonium hydroxide (80:20:3)until the solvent front has moved at least 15cm.Remove the plate from the chamber,air-dry,and view under short-wavelength UVlight:trimethoprim produces a spot at about RF0.7,and the trimethoprim degradation product can be seen at RF0.3to 0.5.Any spot from the Test solutionat about RF0.3to 0.5is not greater in size and intensity than the spot produced by Standard solution Bat about RF0.7,corresponding to not more than 0.5%.
LIMIT OF SULFANILAMIDE,SULFANILIC ACID,AND SULFAMETHOXAZOLEN4-GLUCOSIDE)—
Alcohol–methanol mixture— Mix dehydrated alcohol and methanol (95:5).
Modified Ehrlich's reagent— Dissolve 100mg of p-dimethylaminobenzaldehyde in 1mLof hydrochloric acid,and dilute with alcohol to 100mL.
Test solution— Using a syringe,transfer an accurately measured volume of Oral Suspension,equivalent to 200mg of sulfamethoxazole,to a 100-mLvolumetric flask containing 10mLof ammonium hydroxide;and add 50mLof methanol.Shake for 3minutes,and dilute with methanol to volume.Centrifuge a portion of the solution for 3minutes.
Standard solution A— Weigh 20mg of USP Sulfamethoxazole RSinto a 10-mLvolumetric flask,dissolve in 1mLof ammonium hydroxide,dilute with methanol to volume,and mix.
Standard solution B— Weigh 10mg of USP Sulfanilamide RSinto a 50-mLvolumetric flask,dissolve in 5mLof ammonium hydroxide,and dilute with methanol to volume.Pipet 5mLof this solution into a 100-mLvolumetric flask,add 10mLof ammonium hydroxide,and dilute with methanol to volume.
Standard solution C— Weigh 10mg of USP Sulfanilic Acid RSinto a 50-mLvolumetric flask,dissolve in 5mLof ammonium hydroxide,and dilute with methanol to volume.Pipet 3mLof this solution into a 100-mLvolumetric flask,add 10mLof ammonium hydroxide,and dilute with methanol to volume.
Standard solution D— Weigh 3.0mg of USP Sulfamethoxazole N4-Glucoside RSinto a 50-mLvolumetric flask,dissolve in 5mLof ammonium hydroxide,and dilute with methanol to volume.
Procedure— Apply 50µLeach of the Test solutionand Standard solutions A,B,C,and Dto separate points on a thin-layer chromatographic plate (see Chromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel.Place the plate in an unsaturated chromatographic chamber,and develop the chromatogram in a solvent system consisting of a mixture of Alcohol–methanol mixture,heptane,chloroform,and glacial acetic acid (25:25:25:7)until the solvent front has moved at least 12cm.Remove the plate from the developing chamber,air-dry,spray with Modified Ehrlich's reagent,and allow the plate to stand for 15minutes:sulfamethoxazole produces a spot at about RF0.7.Any spots from the Test solutionat about RF0.5,0.1,and 0.3are not greater in size and intensity than spots produced by Standard solutions B,C,and D,respectively,corresponding to not more than 0.5%of sulfanilamide,0.3%of sulfanilic acid,and 3.0%of sulfamethoxazole N4-glucoside.
Alcohol content,Method IIá611ñ: not more than 0.5%of C2H5OH.
Assay—
Mobile phase— Mix 1400mLof water,400mLof acetonitrile,and 2.0mLof triethylamine in a 2000-mLvolumetric flask.Allow to equilibrate to room temperature,and adjust with 0.2Nsodium hydroxide or dilute glacial acetic acid (1in 100)to a pHof 5.9±0.1.Dilute with water to volume,and filter through a 0.45-µm membrane,making adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).
Standard preparation— Dissolve accurately weighed quantities of USP Trimethoprim RSand USP Sulfamethoxazole RSin methanol,and quantitatively dilute with methanol to obtain a solution containing,in each mL,about 0.32mg and 0.32Jmg,respectively,Jbeing the ratio of the labeled amount,in mg,of sulfamethoxazole to the labeled amount,in mg,of trimethoprim in the dosage form.Transfer 5.0mLof this solution to a 50-mLvolumetric flask,dilute with Mobile phaseto volume,and mix to obtain a Standard preparationhaving known concentrations of about 0.032mg of USP Trimethoprim RSper mLand 0.032Jmg of USP Sulfamethoxazole RSper mL.
Assay preparation— Transfer an accurately measured volume of Oral Suspension,equivalent to about 80mg of Sulfamethoxazole,to a 50-mLvolumetric flask with the aid of about 30mLof methanol.Sonicate the mixture for about 10minutes with occasional shaking.Allow to equilibrate to room temperature,dilute with methanol to volume,mix,and centrifuge.Transfer 5.0mLof the supernatant to a second 50-mLvolumetric flask,dilute with Mobile phaseto volume,mix,and filter.
Chromatographic system(see Chromatography á621ñ)— The liquid chromatograph is equipped with a 254-nm detector and a 3.9-mm ×30-cm column that contains packing L1.The flow rate is about 2mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the relative retention times are about 1.0for trimethoprim and 1.8for sulfamethoxazole;the resolution,R,between sulfamethoxazole and trimethoprim is not less than 5.0;the tailing factor for the trimethoprim and sulfamethoxazole peaks is not more than 2.0;and the relative standard deviation for replicate injections is not more than 2.0%.
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 each mLof the Oral Suspension taken by the formula:
(500C/V)(rU/rS),
in which Cis the concentration,in mg per mL,of the appropriate USP Reference Standard in the Standard preparation;Vis the volume,in mL,of Oral Suspension taken;and rUand rSare the peak 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 1830
Pharmacopeial Forum:Volume No.29(6)Page 1990
Phone Number:1-301-816-8394