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

USP Reference standards 11— USP Neomycin Sulfate RS. USP Polymyxin B Sulfate RS.

Thin-layer chromatographic identification test 201BNP: meets the requirements.

Minimum fill 755: meets the requirements.

Residual solvents 467: meets the requirements.

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 No. 3. Combine the aqueous extracts, and dilute with Buffer No. 3 to an appropriate volume to obtain a stock solution of convenient concentration. Dilute this stock solution quantitatively and stepwise with Buffer No. 3 to obtain a Test Dilution having a concentration assumed to be equal to the median dose level of the Standard.

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 No. 6. Combine the aqueous extracts, and dilute with Buffer No. 6 to an appropriate volume to obtain a stock solution. Dilute this stock solution quantitatively and stepwise with Buffer No. 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 No. 6, to obtain the same concentration of neomycin present in the Test Dilution.

Expert Committee : (MDANT05) Monograph Development-Antibiotics

USP29–NF24 Page 1501

Phone Number : 1-301-816-8223