Packaging and storage—
Preserve in tight, light-resistant containers.
Labeling—
Where packaged for prescription compounding, the label states the number of Polymyxin B Units in the container and per milligram, that it is not intended for manufacturing use, that it is not sterile, and that its potency cannot be assured for longer than 60 days after opening. Where it is intended for use in preparing injectable or other sterile dosage forms, the label states that it is sterile or must be subjected to further processing during the preparation of injectable or other sterile dosage forms.
Identification—
A:
Liquid Chromatographic Identification Test—
Mobile phase—
Prepare a mixture of 0.1 M tribasic sodium phosphate and acetonitrile (77:23), and adjust with phosphoric acid to a pH of 3.0. Make adjustments if necessary (see
System Suitability under
Chromatography 
621
.
Standard solution—
Prepare a solution of
USP Polymyxin B Sulfate RS in
Mobile phase having a concentration of about 3.5 mg per mL. Protect this solution from light.
Test solution—
Prepare a solution of Polymyxin B Sulfate in Mobile phase having a concentration of about 3.5 mg per mL. Protect this solution from light.
Chromatographic system (see Chromatography 621)—
The liquid chromatograph is equipped with a 212-nm detector and a 4.6-mm × 25-cm column that contains 5-µm packing L1. The flow rate is about 1 mL per minute.
Procedure—
Separately inject equal volumes (about 10 µL) of the Standard solution and the Test solution into the chromatograph, and record the chromatograms. The chromatogram obtained from the Test solution corresponds qualitatively to that obtained from the Standard solution, exhibiting a major peak corresponding to polymyxin B1 and peaks at relative retention times of about 0.5 (polymyxin B2) and 0.6 (polymyxin B3).
B:
Dissolve 2 mg in 5 mL of water, add 5 mL of 2.5 N sodium hydroxide, mix, and add 5 drops of cupric sulfate solution (1 in 100), shaking after the addition of each drop: a reddish violet color is produced.
C:
A solution (1 in 20) meets the requirements of the tests for
Sulfate 191.
pH 791:
between 5.0 and 7.5, in a solution containing 5 mg per mL.
Loss on drying 731—
Dry about 100 mg, accurately weighed, in a capillary-stoppered bottle in vacuum at 60
for 3 hours: it loses not more than 7.0% of its weight.
Content of phenylalanine—
Transfer about 0.375 g of Polymyxin B Sulfate, accurately weighed, to a 100-mL volumetric flask, dissolve in and dilute with 0.1 N hydrochloric acid to volume, and mix. Measure the absorbances of this solution at the maxima at about 264 nm (
A264), 258 nm (
A258), and 252 nm (
A252), and the absorbances at 280 nm (
A280) and 300 nm (
A300). Calculate the percentage of phenylalanine in the portion of Polymyxin B Sulfate taken by the formula:
(9.4787/W)(A258 – 0.5A252 + 0.5A264 – 1.84A280 + 0.8A300),
in which
W is the weight, in g, of Polymyxin B Sulfate taken: it contains between 9% and 12% of phenylalanine, calculated on the dried basis.
Other requirements—
If for prescription compounding, it meets the requirements for
Residue on ignition under
Polymyxin B for Injection. Where the label states that Polymyxin B Sulfate is sterile, it meets the requirements for
Sterility Tests 71 and, where intended for injectable dosage forms, for
Pyrogen under
Polymyxin B for Injection. Where the label states that Polymyxin B Sulfate must be subjected to further processing during the preparation of injectable dosage forms, it meets the requirements for
Pyrogen under
Polymyxin B for Injection.
Auxiliary Information—
Staff Liaison :
Brian D. Gilbert, Ph.D., Scientist
Expert Committee : (MDANT05) Monograph Development-Antibiotics
USP29–NF24 Page 1750
Pharmacopeial Forum : Volume No. 28(4) Page 1183
Phone Number : 1-301-816-8223
