Neomycin and Polymyxin B Sulfates and Lidocaine Cream

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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Neomycin and Polymyxin B Sulfates and Lidocaine Cream contains the equivalent of not less than 90.0 percent and not more than 130.0 percent of the labeled amounts of neomycin and polymyxin B, and not less than 90.0 percent and not more than 110.0 percent of the labeled amount of lidocaine (C₁₄H₂₂N₂O).

Packaging and storage-Preserve in well-closed containers, preferably at controlled room temperature.

USP REFERENCE STANDARDS (11)-

USP Lidocaine RS

USP Neomycin Sulfate RS

USP Polymyxin B Sulfate RS

1 Identification

A: It meets the requirements under Thin-Layer Chromatographic Identification Test (201BNP)

B: The retention time of the major peak for lidocaine in the chromatogram of the Assay preparation corresponds to that in the chromatogram of the Standard preparation, as obtained in the Assay for lidocaine.

MINIMUM FILL (755): meets the requirements.

Change to read:

Assay for neomycin-Proceed as directed under Antibiotics-Microbial Assays (81), using an accurately weighed portion of Cream, equivalent to about 1.75 mg of neomycin, shaken in a separator with about 50 mL of ether, and extracted with four 20-mL portions of Buffer B.3. Combine the aqueous extracts, and dilute with Buffer B.3 to an appropriate volume to obtain a stock solution of convenient concentration. Dilute this stock solution quantitatively and stepwise with Buffer B.3 to obtain a Test Dilution having a concentration assumed to be equal to the median dose level of the Standard _{(ERR 1-Jul-2024)}

Change to read:

Assay for polymyxin B-Proceed as directed under Antibiotics-Microbial Assays (81), using an accurately weighed portion of Cream shaken with about 50 mL of ether in a separator, and extracted with four 25-mL portions of Buffer B.6. Combine the aqueous extracts, and dilute with Buffer B.6 to an appropriate volume to obtain a stock solution. Dilute this stock solution quantitatively and stepwise with Buffer B.6 to obtain a Test Dilution having a concentration assumed to be equal to the median dose level of the Standard (10 Polymyxin B Units per mL). Add to each test dilution of the Standard a quantity of USP Neomycin Sulfate RS, dissolved in Buffer B.6, to obtain the same concentration of neomycin present in the Test Dilution _{(ERR 1-Jul-2024)}

2 Assay for lidocaine

Mobile phase, Standard preparation, and Chromatographic system-Proceed as directed in the Assay for lidocaine under Neomycin and Polymyxin B Sulfates, Bacitracin, and Lidocaine Ointment.

Assay preparation-Using Cream, proceed as directed for the Assay preparation in the Assay for lidocaine under Neomycin and Polymyxin B. Sulfates, Bacitracin, and Lidocaine Ointment.

Procedure-Proceed as directed for Procedure in the Assay for lidocaine under Neomycin and Polymyxin B Sulfates, Bacitracin, and Lidocaine Ointment. Calculate the quantity, in mg, of lidocaine (C₁₄H₂₂N₂O) in the portion of Cream taken by the formula:

100C(r_u /r_s )

in which C is the concentration, in mg per mL, of USP Lidocaine RS in the Standard preparation; and r_u and r_s are the lidocaine peak responses obtained from the Assay preparation and the Standard preparation, respectively.