Polymyxin B Sulfate and Bacitracin Zinc Topical Aerosol
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This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition
Issued and maintained by the United States Pharmacopeial Convention (USP)
Polymyxin B Sulfate and Bacitracin Zinc Topical Aerosol contains the equivalent of not less than 90.0 percent and not more than 130.0 percent of the labeled amounts of polymyxin B and bacitracin.
Packaging and storage—Preserve in pressurized containers, and avoid exposure to excessive heat.
Identication—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 Identication Test 〈201BNP〉. The specied 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 Specied Microorganisms 〈62〉.
Water Determination, 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 Topical Aerosols 〈603〉.
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 ask 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 B.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 B.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.]
