Dantrolene Sodium

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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1 DEFINITION 

Dantrolene Sodium contains NLT 90.0% and NMT 96.0% of dantrolene (C₁₄H₁₀N₄O₅), the free acid form of Dantrolene Sodium, calculated on the anhydrous basis. 

2 IDENTIFICATION 

Change to read: 

A. Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197K (CN 1-May-2020) 

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

C. Identification Tests—General 〈191〉, Sodium 

Sample solution: To 0.1 g of Dantrolene Sodium, add 20 mL of water and 2 drops of acetic acid, shake well, and pass the resulting solution through a suitable lter. Use 2 mL of the ltrate. 

Analysis 

Sample: Sample solution 

Acceptance criteria: Meets the requirements 

D. 

Solution A: Dissolve 2.7 g of methoxyphenylacetic acid in 6 mL of tetramethylammonium hydroxide TS, and add 20 mL of dehydrated alcohol. Solution B: 158 mg/mL of ammonium carbonate in water 

Sample solution: To 0.1 g of Dantrolene Sodium, add 20 mL of water and 2 drops of acetic acid, shake well, and pass the resulting solution through a suitable lter. Use the ltrate. 

Analysis 

Sample: Sample solution 

Part 1: To 0.5 mL of the Sample solution in a suitable container, add 1.5 mL of Solution A, and cool in ice water for 30 min. Part 2: Transfer the container from Part 1 to a water bath at 20°, and stir for 5 min. 

Part 3: Add 1 mL of ammonia TS to the container from Part 2. 

Part 4: Add 1 mL of Solution B to the container from Part 3. 

Acceptance criteria: The requirements for Part 1, Part 2, Part 3, and Part 4 must all be met. 

Part 1: A voluminous, white, crystalline precipitate is formed. 

Part 2: The precipitate does not disappear. 

Part 3: The precipitate dissolves completely. 

Part 4: No precipitate is formed. 

3 ASSAY 

3.1 Procedure 

Buffer: Dissolve 3.85 g of ammonium acetate in 1.0 L of water; adjusted with glacial acetic acid to a pH of 4.5 ± 0.1. Solution A: Acetonitrile, Buffer, and water (10:20:70) 

Solution B: Acetonitrile and Buffer (80:20) 

Mobile phase: See Table 1. 

Table 1 

Diluent: Acetonitrile and water (50:50) 

System suitability stock solution A: 1.25 mg/mL of USP Dantrolene Sodium RS prepared as follows. Transfer a suitable amount of USP Dantrolene Sodium RS to an appropriate volumetric ask. Dissolve in 5% of the total ask volume of dimethylformamide. Add 5% of the total ask volume of glacial acetic acid, and dilute with acetone to volume. 

System suitability stock solution B: 0.125 mg/mL each of USP Dantrolene Related Compound B RS and USP Dantrolene Related Compound C RS prepared as follows. Transfer suitable amounts of USP Dantrolene Related Compound B RS and USP Dantrolene Related Compound C RS to an appropriate volumetric ask. Dissolve in 5% of the total ask volume of dimethylformamide. Add 5% of the total ask volume of glacial acetic acid, and dilute with acetone to volume. 

System suitability solution: 125 µg/mL of USP Dantrolene Sodium RS from System suitability stock solution A and 2.5 µg/mL each of USP Dantrolene Related Compound B RS and USP Dantrolene Related Compound C RS from System suitability stock solution B in Diluent Standard stock solution: 1.0 mg/mL of USP Dantrolene RS prepared as follows. Transfer a suitable amount of USP Dantrolene RS to an appropriate volumetric ask. Dissolve in 5% of the total ask volume of dimethylformamide. Add 5% of the total ask volume of glacial acetic acid, and dilute with acetone to volume. 

Standard solution: 100 µg/mL of USP Dantrolene RS from Standard stock solution in Diluent 

Sample stock solution: 1.25 mg/mL of Dantrolene Sodium prepared as follows. Transfer a suitable amount of Dantrolene Sodium to an appropriate volumetric ask. Dissolve in 5% of the total ask volume of dimethylformamide. Add 5% of the total ask volume of glacial acetic acid, and dilute with acetone to volume. 

Sample solution: 125 µg/mL of Dantrolene Sodium from Sample stock solution in Diluent 

Chromatographic system 

(See Chromatography 〈621〉, System Suitability.) 

Mode: LC 

Detector: UV 365 nm 

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

Flow rate: 2 mL/min 

Injection volume: 20 µL 

System suitability 

Samples: System suitability solution and Standard solution 

[Note—The relative retention times for dantrolene related compound B, dantrolene, and dantrolene related compound C are 0.68, 1.0, and 1.24, respectively.] 

Suitability requirements 

Resolution: NLT 8 between dantrolene related compound C and dantrolene, System suitability solution 

Tailing factor: NMT 1.5, Standard solution 

Relative standard deviation: NMT 1.0%, Standard solution 

Analysis 

Samples: Standard solution and Sample solution 

Calculate the percentage of dantrolene (C₁₄H₁₀N₄O₅) in the portion of Dantrolene Sodium taken: 

Result = (r_u/r_s) × (C_s/C_u) × 100  

r_u = peak response of dantrolene from the Sample solution 

r_s = peak response of dantrolene from the Standard solution 

C_s = concentration of USP Dantrolene RS in the Standard solution (µg/mL)  

C_u = concentration of Dantrolene Sodium in the Sample solution (µg/mL) 

Acceptance criteria: 90.0%–96.0% on the anhydrous basis 

4 IMPURITIES 

4.1 Limit of Dantrolene Related Compound A 

Mobile phase: Acetonitrile and water (80:20) 

Standard stock solution: 17.5 µg/mL of USP Dantrolene Related Compound A RS and 50 µg/mL of USP Dantrolene Sodium RS in dimethylformamide 

Standard solution: 0.35 µg/mL of USP Dantrolene Related Compound A RS and 1 µg/mL of USP Dantrolene Sodium RS from Standard stock solution in acetonitrile 

Sample stock solution: 1.25 mg/mL of Dantrolene Sodium prepared as follows. Transfer a suitable amount of Dantrolene Sodium to an appropriate volumetric ask. Dissolve in 5% of the total ask volume of dimethylformamide. Add 5% of the total ask volume of glacial acetic acid, and dilute with acetone to volume. 

Sample solution: 175 µg/mL of Dantrolene Sodium from Sample stock solution in acetonitrile 

Chromatographic system 

(See Chromatography 〈621〉, System Suitability.) 

Mode: LC 

Detector: UV 365 nm 

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

Flow rate: 1 mL/min 

Injection volume: 20 µL 

System suitability 

Sample: Standard solution 

[Note—The dantrolene peak elutes at void volume at approximately 1.5 min.] 

Suitability requirements 

Tailing factor: NMT 1.5 for dantrolene related compound A 

Relative standard deviation: NMT 5% for dantrolene related compound A 

Analysis 

Samples: Standard solution and Sample solution 

Calculate the percentage of dantrolene related compound A in the portion of Dantrolene Sodium taken: 

Result = (r_u/r_s) × (C_s/C_u) × 100 

r_u = peak response of dantrolene related compound A from the Sample solution 

r_s = peak response of dantrolene related compound A from the Standard solution 

C_s = concentration of USP Dantrolene Related Compound A RS in the Standard solution (µg/mL) 

C_u = concentration of Dantrolene Sodium in the Sample solution (µg/mL) 

Acceptance criteria: NMT 0.15% 

4.2 Organic Impurities 

Mobile phase, Diluent, System suitability stock solution B, System suitability solution, Sample solution, and Chromatographic system: Proceed as directed in the Assay. 

Standard solution A: Use the Standard solution from the Assay. 

Standard solution B: 0.25 µg/mL each of USP Dantrolene Related Compound B RS and USP Dantrolene Related Compound C RS from System suitability stock solution B in Diluent 

System suitability 

Samples: System suitability solution and Standard solution A 

[Note—The relative retention times for dantrolene related compound B, dantrolene, and dantrolene related compound C are 0.68, 1.0, and 1.24, respectively.] 

Suitability requirements 

Resolution: NLT 8 between dantrolene related compound C and dantrolene, System suitability solution 

Tailing factor: NMT 1.5, Standard solution A 

Relative standard deviation: NMT 1.0%, Standard solution A 

Analysis 

Samples: Sample solution and Standard solution B 

Calculate the percentage of dantrolene related compound B and dantrolene related compound C in the portion of Dantrolene Sodium taken: 

Result = (r_u/r_s) × (C_s/C_u) × 100 

r_u = peak response of dantrolene related compound B or dantrolene related compound C from the Sample solution 

r_s = peak response of dantrolene related compound B or dantrolene related compound C from Standard solution B 

C_s = concentration of USP Dantrolene Related Compound B RS or USP Dantrolene Related Compound C RS in Standard solution B (µg/mL) 

C_u = concentration of Dantrolene Sodium in the Sample solution (µg/mL) 

Acceptance criteria 

Dantrolene related compound B: NMT 0.50% 

Dantrolene related compound C: NMT 0.30% 

5 SPECIFIC TESTS 

Water Determination 〈921〉, Method Ia: 14.5%–17.0% 

6 ADDITIONAL REQUIREMENTS 

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

USP Reference Standards 〈11〉 

USP Dantrolene RS 

1-({[5-(4-Nitrophenyl)furan-2-yl]methylene}amino)imidazolidine-2,4-dione. 

C H N O 314.25 

14 10 4 5 

USP Dantrolene Sodium RS 

USP Dantrolene Related Compound A RS 

1,2-Bis{[5-(4-nitrophenyl)furan-2-yl]methylene}hydrazine; 

Also known as 5-(4-Nitrophenyl)furaldehyde azine. 

C₁₄H₁₀N₄O₅       430.38 

USP Dantrolene Related Compound B RS 

N-Carbamoyl-N-({[5-(4-nitrophenyl)furan-2-yl]methylene}amino)glycine; 

Also known as 5-(4-Nitrophenyl)-2-furaldehyde-2-carboxymethyl semicarbazone. 

C₁₄H₁₂N₄O₆        332.27 

USP Dantrolene Related Compound C RS 

5-(4-Nitrophenyl)furan-2-carbaldehyde. 

C₁₁H₇NO₄       217.18