Bacitracin Zinc and Polymyxin B Sulfate Ointment
» Bacitracin Zinc and Polymyxin B Sulfate Ointment contains the equivalent of not less than 90.0 percent and not more than 130.0 percent of the labeled amounts of bacitracin and polymyxin B. It may contain a suitable local anesthetic.
Packaging and storage— Preserve in well-closed, light-resistant containers.
Minimum fill 755: meets the requirements.
Water, 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.
Assay for bacitracin— Proceed with Ointment as directed in the Assay under Bacitracin Zinc Ointment.
Assay for polymyxin B— Proceed as directed for polymyxin B under Antibiotics—Microbial Assays 81, using an accurately weighed portion of Ointment shaken with about 50 mL of ether in a separator, and extracted with four 20-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.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Ahalya Wise, M.S.
(MDANT05) Monograph Development-Antibiotics
Reference Standards Lili Wang, Technical Services Scientist
USP32–NF27 Page 1624
Pharmacopeial Forum: Volume No. 28(4) Page 1071