Clofazimine

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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C₂₇H₂₂Cl₂N₄ 473.40

2-Phenazinamine, N,5-bis(4-chlorophenyl)-3,5-dihydro-3-[(1-methylethyl)imino]-;

3-(p-Chloroanilino)-10-(p-chlorophenyl)-2,10-dihydro-2-(isopropylimino)phenazine

CAS RN®: 2030-63-9; UNII: D959AE5USF.

1 DEFINITION

Clofazimine contains NLT 98.0% and NMT 102.0% of clofazimine (C₂₇H₂₂Cl₂N₄), calculated on the dried basis.

2 IDENTIFICATION

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

B. The retention time of the major peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay.

3 ASSAY

3.1 Procedure

Buffer: 4.5 mg/mL of sodium dodecyl sulfate, 1.7 mg/mL of tetrabutylammonium hydrogen sulfate, and 1.8 mg/mL of disodium hydrogen phosphate in water. Adjust with dilute phosphoric acid (about 8.5%) to a pH of 3.0 in 90% of the volume before diluting with water to volume.

Mobile phase: Acetonitrile and Buffer (65:35)

Standard solution: 0.05 mg/mL of USP Clofazimine RS in Mobile phase

Sample solution: 0.05 mg/mL of Clofazimine in Mobile phase

Chromatographic system

• (See Chromatography 〈621〉, System Suitability.)
• Mode: LC
• Detector: UV 280 nm
• Column: 4.6-mm × 25-cm; 5-µm packing L7
• Flow rate: 1.0 mL/min
• Injection volume: 20 µL

System suitability

• Sample: Standard solution
• Suitability requirements
• Tailing factor: NMT 1.5 for the clofazimine peak, Standard solution
• Relative standard deviation: NMT 0.73% for the clofazimine peak, Standard solution

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of clofazimine (C₂₇H₂₂Cl₂N₄) in the portion of Clofazimine taken:

Result = (r_u/r_s) × (C_s/C_u) × 100

r_u = peak response from the Sample solution

r_s = peak response from the Standard solution

C_s = concentration of USP Clofazimine RS in the Standard solution (mg/mL)

C_u = concentration of Clofazimine in the Sample solution (mg/mL)

Acceptance criteria: 98.0%-102.0% on the dried basis

4 IMPURITIES

4.1 Residue on Ignition 〈281〉: NMT 0.1%

4.2 Organic Impurities

Buffer, Mobile phase, and Chromatographic system: Proceed as directed in the Assay.

System suitability solution: 0.5 mg/mL of USP Clofazimine RS and 1.5 µg/mL of USP Clofazimine Related Compound B RS in Mobile phase

Standard solution: 0.5 µg/mL of USP Clofazimine RS and 5.0 µg/mL of USP Clofazimine Related Compound B RS in Mobile phase

Sample solution: 0.5 mg/mL of Clofazimine in Mobile phase

System suitability

• Samples: System suitability solution and Standard solution
• Suitability requirements
• Resolution: NLT 2.0 between the clofazimine and clofazimine related compound B peaks, System suitability solution
• Relative standard deviation: NMT 2.8% for the clofazimine peak and NMT 2.0% for the clofazimine related compound B peak, Standard solution

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of clofazimine related compound B in the portion of Clofazimine taken:

Result = (r_u/r_s) × (C_s/C_u) × 100

r_u = peak response of clofazimine related compound B from the Sample solution

r_s = peak response of clofazimine related compound B from the Standard solution

C_s = concentration of USP Clofazimine Related Compound B RS in the Standard solution (mg/mL)

C_u = concentration of Clofazimine in the Sample solution (mg/mL)

Calculate the percentage of any individual unspecified impurity in the portion of Clofazimine taken:

Result = (r_u/r_s) × (C_s/C_u) × 100

r_u = peak response of any individual unspecified impurity from the Sample solution

r_s = peak response of clofazimine from the Standard solution

C_s = concentration of USP Clofazimine RS in the Standard solution (mg/mL)

C_u = concentration of Clofazimine in the Sample solution (mg/mL)

Acceptance criteria: See Table 1. Disregard any impurity peaks less than 0.05%.

5 SPECIFIC TESTS

5.1 Loss on Drying 〈731〉

Analysis: Dry a sample at 105° for 3 h.

Acceptance criteria: NMT 0.5%

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight, light-resistant containers at room temperature.

USP Reference Standards 〈11〉

• USP Clofazimine RS
• USP Clofazimine Related Compound B RS

5-(4-Chlorophenyl)-3-(isopropylimino)-N-phenyl-3,5-dihydrophenazin-2-amine.

C₂₇H₂₃ClN₄ 438.95