Packaging and storage— Preserve in pressurized containers,and avoid exposure to excessive heat.

USP Reference standards á11ñ— USP Polymyxin B Sulfate RS.USP Bacitracin Zinc RS.

Identification— Collect in a suitable container the expelled contents of 1Aerosol container,shake with a volume of 0.1Nhydrochloric acid sufficient to obtain a solution containing about 500USP Bacitracin Units per mL,centrifuge,and use the clear supernatant as the test solution.Proceed as directed underThin-Layer Chromatographic Identification Test á201BNPñ.The specified result is observed.

Microbial limits— Collect aseptically in a suitable container half the contents expelled from 5containers,dissolve in 500mLof Fluid Acontaining 0.25g of sodium thioglycollate and adjusted with sodium hydroxide to a pHof 6.6±0.6,pass through a membrane filter as directed for Membrane Filtrationunder Test for Sterility of the Product to be Examined under Sterility Tests á71ñ,except to place the filter on the surface of Soybean–Casein Digest Agar Medium in a Petri dish,incubate for 7days at 30to 35,and count the number of colonies on the filter.Similarly prepare a second specimen,except to incubate at 20to 25.Not more than 20colonies are observed from the two specimens.It meets also the requirements of the tests for absence of Staphylococcus aureusand Pseudomonas aeruginosaunder Microbial Limit Tests á61ñ.

Water,Method Iá921ñ— Store 1container of Topical Aerosol in a freezer for not less than 2hours,open the container,and transfer 10.0mLof the freshly mixed specimen to a titration vessel containing 20mLof a mixture of toluene and methanol (7:3)instead of methanol.In titrating the specimen,determine the endpoint at a temperature of 10or higher:not more than 0.5%of water is found.

Other requirements— It meets the requirements for Pressure Test,Minimum Fill,and Leakage Testunder Aerosols,Metered-Dose Inhalers,and Dry Powder Inhalers á601ñ.

Assay for polymyxin B— Proceed as directed for polymyxin Bunder Antibiotics—Microbial Assays á81ñ,expelling the entire contents of 1container of Topical Aerosol,according to the directions in the labeling,into a 2000-mLconical flask held in a horizontal position.Add 500.0mLof 0.01Nhydrochloric acid,and shake to dissolve.Immediately dilute an accurately measured volume of this acidic solution quantitatively and stepwise with Buffer No.6to obtain a Test Dilutionhaving a concentration of polymyxin Bassumed to be equal to the median dose level of the Standard.

Assay for bacitracin— Proceed as directed for bacitracin under Antibiotics—Microbial Assays á81ñ,using an accurately measured volume of the acidic solution obtained in the Assay for polymyxin Bimmediately diluted quantitatively and stepwise with Buffer No.1to yield a Test Dilutionhaving a bacitracin concentration assumed to be equal to the median dose level of the Standard.[NOTE—Add additional hydrochloric acid to each test dilution of the Standard to obtain the same concentration of hydrochloric acid as in the Test Dilution.]

Expert Committee:(PA7)Pharmaceutical Analysis 7

USP28–NF23Page 1577

Phone Number:1-301-816-8335