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

USP Reference standards 11—
USP Polymyxin B Sulfate RS.
USP Bacitracin Zinc RS.

Identification— Collect in a suitable container the expelled contents of 1 Aerosol container, shake with a volume of 0.1 N hydrochloric acid sufficient to obtain a solution containing about 500 USP Bacitracin Units per mL, centrifuge, and use the clear supernatant as the test solution. Proceed as directed under Thin-Layer Chromatographic Identification Test 201BNP. The specified result is observed.

Microbial enumeration tests 61 and Tests for specified microorganisms 62— Collect aseptically in a suitable container half the contents expelled from 5 containers, dissolve in 500 mL of Fluid A containing 0.25 g of sodium thioglycollate and adjusted with sodium hydroxide to a pH of 6.6 ± 0.6, pass through a membrane filter as directed for Membrane Filtration under Test for Sterility of the Product to be Examined under Sterility Tests 71, except to place the filter on the surface of Soybean–Casein Digest Agar Medium in a Petri dish, incubate for 7 days at 30 to 35, and count the number of colonies on the filter. Similarly prepare a second specimen, except to incubate at 20 to 25. Not more than 20 colonies are observed from the two specimens. It meets also the requirements of the tests for absence of Staphylococcus aureus and Pseudomonas aeruginosa under Microbial Enumeration Tests 61 and Tests for Specified Microorganisms 62.

Water, Method I 921— Store 1 container of Topical Aerosol in a freezer for not less than 2 hours, open the container, and transfer 10.0 mL of the freshly mixed specimen to a titration vessel containing 20 mL of a mixture of toluene and methanol (7:3) instead of methanol. In titrating the specimen, determine the endpoint at a temperature of 10 or higher: not more than 0.5% of water is found.

Other requirements— It meets the requirements for Pressure Test, Minimum Fill, and Leakage Test under Aerosols, Metered-Dose Inhalers, and Dry Powder Inhalers 601.

Assay for polymyxin B— Proceed as directed for polymyxin B under Antibiotics—Microbial Assays 81, expelling the entire contents of 1 container of Topical Aerosol, according to the directions in the labeling, into a 2000-mL conical flask held in a horizontal position. Add 500.0 mL of 0.01 N hydrochloric acid, and shake to dissolve. Immediately dilute an accurately measured volume of this acidic solution quantitatively and stepwise with Buffer No. 6 to obtain a Test Dilution having a concentration of polymyxin B assumed to be equal to the median dose level of the Standard.

Assay for bacitracin— Proceed as directed for bacitracin under Antibiotics—Microbial Assays 81, using an accurately measured volume of the acidic solution obtained in the Assay for polymyxin B immediately diluted quantitatively and stepwise with Buffer No. 1 to yield a Test Dilution having 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.]

Topic/Question	Contact	Expert Committee
Monograph	Ahalya Wise, M.S. Scientist 1-301-816-8161	(MDANT05) Monograph Development-Antibiotics
Reference Standards	Lili Wang, Technical Services Scientist 1-301-816-8129 RSTech@usp.org
61	Radhakrishna S Tirumalai, Ph.D. Senior Scientist 1-301-816-8339	(MSA05) Microbiology and Sterility Assurance
62	Radhakrishna S Tirumalai, Ph.D. Senior Scientist 1-301-816-8339	(MSA05) Microbiology and Sterility Assurance

USP32–NF27 Page 3327