Colistin Sulfate

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

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

DOWNLOAD PDF HERE

Colistin, sulfate;

Colistins sulfate

CAS RN®: 1264-72-8; UNII: WP15DXU577.

1 DEFINITION

Colistin Sulfate is the sulfate salt of an antibacterial substance produced by the growth of Bacillus polymyxa var. colistinus. It has a potency equivalent to NLT 500 µg of colistin/mg.

2 IDENTIFICATION

Delete the following:

A. Procedure

Add the following:

A. Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197A or 197K

B. Identification Tests-General 〈191〉, Chemical Identification Tests, Sulfate: Meets the requirements

Delete the following:

C. Liquid Chromatographic Identification Test

Add the following:

C. The retention times of the colistin A and colistin B peaks of the Sample solution correspond to those of the Standard solution, as obtained in the test for Composition.

3 ASSAY

Change to read:

3.1 Procedure

Analysis: Proceed as directed for Colistin in Antibiotics-Microbial Assays 〈81〉.

Acceptance criteria: NLT 500 µg of colistin/mg

Add the following:

4 IMPURITIES

4.1 Organic Impurities

Solution A: 4.5 g of anhydrous sodium sulfate in 900 mL of water, adjusted with diluted phosphoric acid to a pH of 2.4 and diluted with water to 1000 mL

Mobile phase: Solution A and acetonitrile (78:22)

Diluent: Water and acetonitrile (80:20)

Sensitivity solution: 5 µg/mL of USP Colistin Sulfate RS in Diluent

Standard solution: 0.5 mg/mL of USP Colistin Sulfate RS in Diluent

Sample solution: 0.5 mg/mL of Colistin Sulfate in Diluent

Chromatographic system

• (See Chromatography (621), System Suitability.)
• Mode: LC
• Detector: UV 215 nm
• Column: 4.6-mm × 25-cm; 3-µm packing L1
• Column temperature: 50°
• Flow rate: 1.0 mL/min
• Injection volume: 20 µL

System suitability

• Samples: Sensitivity solution and Standard solution
• [NOTE-See Table 1 for the relative retention times. Use the reference chromatogram provided with the lot of USP Colistin Sulfate RS to identify the peaks.]
• Suitability requirements
• Peak-to-valley ratio: NLT 1.1 for the ratio of the height of the peak that immediately follows the colistin B peak to the height of the valley. between the two peaks, Standard solution
• Resolution: NLT 2.0 between polymyxin E6 and 7-L-isoleucinepolymyxin E2; NLT 3.0 between 2,3-dehydro colistin A and colistin A, Standard solution
• Signal-to-noise ratio: NLT 10 for the colistin A peak, Sensitivity solution

Analysis

Sample: Sample solution

Calculate the percentage of each individual impurity (for peaks other than colistin A; colistin B; polymyxins E3, E4, E6, E7; 7-L-valinepolymyxin E2; 7-L-isoleucinepolymyxin E2; 7-1-norvalinepolymyxin E1; colistin III; and 2,3-dehydro colistin A) in the portion of Colistin Sulfate taken:

Result = (r_U/r_T) × (1/F) × 100

r_U = peak response of each individual impurity

r_T = sum of all the peak responses

F = relative response factor

Reporting threshold: 0.35%

Acceptance criteria: See Table 1. The reporting threshold is 0.35%.

a N²-(6-Methyl-1-oxoheptyl-l-2,4-diaminobutanoyl-l-threonyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-d-leucyl-l- valyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-l-threonine, cyclic (10→4)-peptide.

b N²-(1-Oxoheptyl)-l-2,4-diaminobutanoyl-l-threonyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-d-leucyl-l-leucyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-l threonine, cyclic (10→4)-peptide.

c N²-[(6S)-3-Hydroxyl-6-methyl-1-oxooctyl]-l-2,4-diaminobutanoyl-l-threonyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-d-leucyl-l-leucyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-l-threonine, cyclic (10→4)-peptide.

d N²-(6-Methyl-1-oxoheptyl-l-2,4-diaminobutanoyl-l-threonyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-d-leucyl-l-isoleucyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-l-threonine, cyclic (10→4)-peptide.

e N²-(6-Methyl-1-oxoheptyl)-l-2,4-diaminobutanoyl-l-threonyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-d-leucyl-l-leucyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-l-threonine, cyclic (10→4)-peptide.

f N²-(1-Oxooctyl)-l-2,4-diaminobutanoyl-l-threonyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-d-leucyl-l-leucyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-l-threonine, cyclic (10→4)-peptide.
g N²-[(S)-6-Methyl-1-oxooctyl]-l-2,4-diaminobutanoyl-l-threonyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-d-leucyl-l-norvalyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-l-threonine, cyclic (10→4)-peptide.

h N²-[(S)-6-Methyl-1-oxooctyl]-l-2,4-diaminobutanoyl-l-threonyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-d-leucyl-l-isoleucyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-l-threonine, cyclic (10→4)-peptide.

i N²-[(S,E)-6-Methyloct-2-enoyl]-l-2,4-diaminobutanoyl-l-threonyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-d-leucyl-l-leucyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-l-threonine, cyclic (10→4)-peptide.

j N²-[(S)-6-Methyl-1-oxooctyl]-l-2,4-diaminobutanoyl-l-threonyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-d-leucyl-l-leucyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-l-threonine, cyclic (10→4)-peptide.

k N²-(7-Methyl-1-oxooctyl)-l-2,4-diaminobutanoyl-l-threonyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-d-leucyl-l-leucyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-l-threonine, cyclic (10→4)-peptide.

l N²-[(S)-6-Methyl-1-oxooctyl]-l-2,4-diaminobutanoyl-l-threonyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-4-[(S)-2-aminobutanoyl]-d-leucyl-l-leucyl-l-2,4-diaminobutanoyl-l-2,4-diaminobutanoyl-l-threonine, cyclic (10→4)-peptide.

5 SPECIFIC TESTS

5.1 pH 〈791〉

4.0–7.0, in 10 mg/mL solution

5.2 Loss on Drying 〈731〉

Sample: 100 mg

Analysis: Dry in a capillary-stoppered bottle under vacuum at a pressure NMT 5 mm of mercury at 60° for 3 h.

Sample: It loses NMT 7.0% of its weight.

Add the following:

5.3 COMPOSITION

Solution A, Mobile phase, Diluent, Sensitivity solution, Standard solution, Sample solution, Chromatographic system, and System suitability: Proceed as directed in the test for Organic Impurities.

Analysis

Sample: Sample solution

Calculate the percentage of each individual component (colistin A; colistin B; polymyxins E3, E4, E6, E7; 7-L-valinepolymyxin E2; 7-L-isoleucinepolymyxin E2; 7-1-norvalinepolymyxin E1; colistin III; and 2,3-dehydro colistin A) in the portion of Colistin Sulfate taken:

Result = (r_U/r_T) × (1/F) × 100

r_U = peak response of each individual component

r_T = sum of all the peak responses

F = relative response factor

Acceptance criteria: See Table 1 (USP 1-Dec-2022)

6 ADDITIONAL REQUIREMENTS

PACKAGING AND STORAGE: Preserve in tight containers.

USP REFERENCE STANDARDS (11)

USP Colistin Sulfate RS