Neomycin and Polymyxin B Sulfates,Bacitracin,and Lidocaine Ointment
»Neomycin and Polymyxin B Sulfates,Bacitracin,and Lidocaine Ointment contains the equivalent of not less than 90.0percent and not more than 130.0percent of the labeled amounts of neomycin,polymyxin B,and bacitracin,and not less than 90.0percent and not more than 110.0percent of the labeled amount of lidocaine (C14H22N2O).
Packaging and storage— Preserve in well-closed containers,preferably at controlled room temperature.
Identification—
A: It meets the requirements under Thin-Layer Chromatographic Identification Test á201BNPñ.
B: The retention time of the major peak for lidocaine in the chromatogram of theAssay preparationcorresponds to that in the chromatogram of theStandard preparation,as obtained in theAssay for lidocaine.
Minimum fill á755ñ: meets the requirements.
Water,Method Iá921ñ: not more than 0.5%,20mLof a mixture of toluene and methanol (7:3)being used in place of methanol in the titration vessel.
Assay for neomycin and Assay for polymyxin B— Proceed with Ointment as directed in theAssay for neomycin and in theAssay for polymyxin BunderNeomycin and Polymyxin B Sulfates and Bacitracin Zinc Ophthalmic Ointment.
Assay for bacitracin— Proceed with Ointment as directed in theAssay underBacitracin Ointment.
Assay for lidocaine—
Mobile phase— Dissolve 4.44g of docusate sodium in 1000mLof a mixture of methanol and water (4:1),add 1mLof 0.1Nsulfuric acid,and mix.Make adjustments if necessary (seeSystem SuitabilityunderChromatography á621ñ).
Standard preparation— Dissolve a suitable quantity of USP Lidocaine RS,accurately weighed,inMobile phase to obtain a solution having a known concentration of about 0.4mg per mL.
Assay preparation— Transfer an accurately weighed quantity of Ointment,equivalent to about 40mg of lidocaine,to a separator,add 50mLofn-hexane,and shake until the specimen is in solution.Add 30mLofMobile phase,shake for 1minute,and allow the layers to separate.Drain the lower layer into a 100-mLvolumetric flask,and extract then-hexane layer remaining in the separator with two 30-mLportions ofMobile phase,combining the lower layers in the volumetric flask.Dilute the combined extracts in the 100-mLvolumetric flask withMobile phase to volume,and mix.
Chromatographic system(see Chromatography á621ñ)— The liquid chromatograph is equipped with a 230-nm detector and a 4-mm ×25-cm column that contains packing L1.The flow rate is about 1mLper minute.Chromatograph theStandard preparation,and record the peak response as directed underProcedure:the column efficiency determined from the analyte peak is not less than 500theoretical plates,and the relative standard deviation for replicate injections is not more than 2.0%.
Procedure— Separately inject equal volumes (about 20µL)of theStandard preparation and theAssay preparation into the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of lidocaine (C14H22N2O)in the portion of Ointment taken by the formula:
100C(rU/rS),
in whichCis the concentration,in mg per mL,of USP Lidocaine RSin theStandard preparation,andrUandrSare the peak responses obtained from theAssay preparation and theStandard preparation,respectively.
Auxiliary Information— Staff Liaison:William W.Wright,Ph.D.,Scientific Fellow
Expert Committee:(PA7)Pharmaceutical Analysis 7
USP28–NF23Page 1353
Pharmacopeial Forum:Volume No.28(4)Page 1161
Phone Number:1-301-816-8335