Riluzole

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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C₈H₅F₃N₂OS  234.20

2-Benzothiazolamine, 6-(trifluoromethoxy)-;

2-Amino-6-(trifluoromethoxy)benzothiazole  CAS RN^®: 1744-22-5; UNII: 7LJ087RS6F.

1 DEFINITION

Riluzole contains NLT 98.0% and NMT 102.0% of the labeled amount of C₈H₅F₃N₂OS, calculated on the anhydrous basis.

2 IDENTIFICATION

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

Mobile phase: Acetonitrile and water (9:11)

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

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

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 221 nm

Column: 4.6-mm × 15-cm; 5-µm packing L1

Flow rate: 2.0 mL/min

Injection size: 20 µL.

[Note—Monitor for 3 times the retention time of riluzole.]

System suitability

Sample: Standard solution

Suitability requirements

Tailing factor: NMT 2.0

Relative standard deviation: NMT 2.0%

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of C₈H₅F₃N₂OS in the portion of Riluzole 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 Riluzole RS in the Standard solution (mg/mL)

C_U = concentration of Riluzole in the Sample solution (mg/mL)

Acceptance criteria: 98.0%–102.0% on the anhydrous basis

4 IMPURITIES

4.1 Inorganic Impurities

Residue on Ignition 〈281〉: NMT 0.1%, a 1.5-g of sample used

4.2 Organic Impurities

Procedure

Mobile phase: Proceed as directed in the Assay.

System suitability solution: 500 µg/mL of USP Riluzole RS and 0.5 µg/mL USP Riluzole Related Compound A RS in Mobile phase

Standard solution: 0.5 µg/mL of USP Riluzole RS in Mobile phase

Sample solution: 500 µg/mL of Riluzole in Mobile phase

Chromatographic system: Proceed as directed in the Assay, and use an injection volume of 100 µL. [Note—Monitor for 11 times the retention time of riluzole.]

System suitability

Samples: System suitability solution and Standard solution

Suitability requirements

Tailing factor: NMT 2.0, Standard solution

Resolution: NLT 1.5 between Riluzole and riluzole related compound A, System suitability solution

Relative standard deviation: NMT 2.0%, Standard solution

Analysis

Samples: Standard solution and Sample solution

Identify the impurities using the relative retention times shown in Impurity Table 1. Calculate the percentage of each impurity in the portion of Riluzole taken:

Result = (r_U/r_S) × (C_S/C_U) × (1/F) × 100

r_U = peak response of the impurity from the Sample solution

r_S = peak response of Riluzole from the Standard solution

C_S = concentration of USP Riluzole RS in the Standard solution (µg/mL)

C_U = concentration of Riluzole in the Sample solution (µg/mL)

F = relative response factor relative to riluzole

Acceptance criteria

Individual impurities: See Impurity Table 1.

Total impurities: NMT 1.0%

Impurity Table 1

ᵃ 4-(Trifluoromethoxy)aniline.

ᵇ 4-Bromo-6-(trifluoromethoxy)benzothiazol-2-amine.

ᶜ 2,6-Dibromo-4-(trifluoromethoxy)aniline.

5 SPECIFIC TESTS

Water Determination, Method I 〈921〉: NMT 0.5%

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in well-closed containers

Change to read:

USP Reference Standards 〈11〉

USP Riluzole RS

USP Riluzole Related Compound A RS

4-(Trifluoromethoxy)aniline. (ERR 1-Apr-2021)

C₇H₆F₃NO  177.13 (ERR 1-Apr-2021)