Neomycin and Polymyxin B Sulfates, Bacitracin Zinc, and Lidocaine Ointment

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, Bacitracin Zinc, and Lidocaine Ointment contains the equivalent of not less than 90.0 percent and not more than 130.0 percent of the labeled amounts of neomycin, polymyxin B, and bacitracin, and not less than 90.0 percent and not more than 110.0 percent of the labeled amount of lidocaine (C₁₄H₂₂N₂O).

1 Packaging and storage

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

1.1 USP Reference standards 〈11〉

USP Bacitracin Zinc RS

USP Lidocaine RS

USP Neomycin Sulfate RS

USP Polymyxin B Sulfate RS

2 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.

Water Determination, Method I 〈921〉: not more than 0.5%, 20 mL of a mixture of toluene and methanol (7:3) being used in place of methanol in the titration vessel.

3 Assay for neomycin

Proceed with Ointment as directed in the Assay for neomycin under Neomycin and Polymyxin B Sulfates and Bacitracin Zinc Ophthalmic Ointment.

4 Assay for polymyxin B

Proceed with Ointment as directed in the Assay for polymyxin B under Neomycin and Polymyxin B Sulfates and Bacitracin Zinc Ophthalmic Ointment.

5 Assay for bacitracin

Proceed with Ointment as directed in the Assay for bacitracin under Neomycin and Polymyxin B Sulfates and Bacitracin Zinc Ophthalmic Ointment.

6 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 the Ointment, proceed as directed for 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 Ointment taken by the formula:

100C(rᵤ/rₛ)

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