Polymyxin B Sulfate and Trimethoprim Ophthalmic Solution
»Polymyxin B Sulfate and Trimethoprim Ophthalmic Solution is a sterile,isotonic,aqueous solution of Polymyxin B Sulfate and Trimethoprim Sulfate or of Polymyxin B Sulfate and Trimethoprim that has been solubilized with Sulfuric Acid.It contains not less than 90.0percent and not more than 130.0percent of the labeled amount of polymyxin Band the equivalent of not less than 90.0percent and not more than 110.0percent of the labeled amount of trimethoprim (C14H18N4O3).It contains one or more preservatives.
Packaging and storage— Preserve in tight,light-resistant containers,and store at controlled room temperature.
Labeling— Label it to indicate that it is to be stored at 15to 25,protected from light.
Identification—
A: It meets the requirements for polymyxin BunderThin-Layer Chromatographic Identification Test á201BNPñ.
B: The retention time of the trimethoprim peak in the chromatogram of theAssay preparation corresponds to that in the chromatogram of theStandard preparation,as obtained in theAssay for trimethoprim.
Sterility á71ñ— It meets the requirements when tested as directed for Membrane Filtrationunder Test for Sterility of the Product to be Examined.
pHá791ñ: between 4.0and 6.2.
Assay for polymyxin B— Proceed as directed for polymyxin Bunder Antibiotics—Microbial Assays á81ñ,using an accurately measured volume of Ophthalmic Solution,diluted quantitatively and stepwise with Buffer No.6,to obtain a Test Dilutionhaving a concentration of polymyxin Bassumed to be equal to the median dose level of the Standard.
Assay for trimethoprim—
Diluent— Prepare a mixture of 0.01Nhydrochloric acid and acetonitrile (870:130).
Mobile phase— Dissolve 1.65g of ethanesulfonic acid in 1000mLof a mixture of water and acetonitrile (870:130).Adjust with 10Nsodium hydroxide or 0.1Nhydrochloric acid to a pHof 3.5.Pass this solution through a filter having a 0.5-µm or finer porosity,and degas.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).
Standard preparation— Dissolve an accurately weighed quantity of USP Trimethoprim RSin Diluentto obtain a solution having a known concentration of about 0.04mg per mL.
Assay preparation— Transfer an accurately measured volume of Ophthalmic Solution,equivalent to about 1mg of trimethoprim,to a 25-mLvolumetric flask,dilute with Diluentto volume,and mix.
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 L11.The flow rate is about 1.5mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the tailing factor is not more than 1.5,when calculated at 10%height of the peak;and the relative standard deviation for replicate injections is not more than 2.0%.
Procedure— Separately inject equal volumes (about 10µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of trimethoprim (C14H18N4O3)in each mLof the Ophthalmic Solution taken by the formula:
25(C/V)(rU/rS),
in which Cis the concentration,in mg per mL,of USP Trimethoprim RSin the Standard preparation;Vis the volume,in mL,of Ophthalmic Solution taken to prepare the Assay preparation;and rUand rSare the trimethoprim peak area responses obtained from the Assay preparationand the Standard preparation,respectively.
Auxiliary Information— Staff Liaison:William W.Wright,Ph.D.,Scientific Fellow
Expert Committee:(PA7)Pharmaceutical Analysis 7
USP28–NF23Page 1578
Pharmacopeial Forum:Volume No.28(4)Page 1185
Phone Number:1-301-816-8335
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