Clobazam

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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C₁₆H₁₃ClN₂O₂ 300.74

1H-1,5-Benzodiazepine-2,4(3H,5H)-dione, 7-chloro-1-methyl-5-phenyl-;

7-Chloro-1-methyl-5-phenyl-1,5-benzodiazepine-2,4-(3H,5H)-dione;

7-Chloro-1-methyl-5-phenyl-1,5-dihydro-2H-benzo[b][1,4]diazepine-2,4(3H)-dione

CAS RN®: 22316-47-8; UNII: 2MRO291B4U.

1 DEFINITION

Clobazam contains NLT 97.0% and NMT 103.0% of clobazam (C₁₆H₁₃ClN₂O₂), calculated on the dried basis.

2 IDENTIFICATION

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

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

Solution A: Transfer 1.0 mL of phosphoric acid to a 1-L volumetric flask containing about 950 mL of water. Dilute with water to volume.

Solution B: Acetonitrile and Solution A (30:70)

Solution C: Acetonitrile and Solution A (80:20)

Mobile phase: See Table 1.

Diluent: Acetonitrile and water (60:40)

Standard stock solution: 0.5 mg/mL of USP Clobazam RS prepared as follows. Transfer a suitable amount of USP Clobazam RS to an appropriate volumetric flask and dissolve in 60% of the flask volume of acetonitrile. Dilute with water to volume.

Standard solution: 0.125 mg/mL of USP Clobazam RS from the Standard stock solution in Diluent

Sample stock solution: 0.5 mg/mL of Clobazam prepared as follows. Transfer a suitable amount of Clobazam to an appropriate volumetric flask and dissolve in 60% of the flask volume of acetonitrile. Dilute with water to volume.

Sample solution: 0.125 mg/mL of Clobazam from the Sample stock solution in Diluent

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

• Mode: LC
• Detector: UV 230 nm
• Column: 4.6-mm × 25-cm; 5-µm packing L1
• Autosampler temperature: 20°
• Flow rate: 1 mL/min
• Injection volume: 5 µL

System suitability

• Sample: Standard solution
• Suitability requirements
• Tailing factor: 0.8–1.5
• Relative standard deviation: NMT 1.10%

Analysis

• Samples: Standard solution and Sample solution
• Calculate the percentage of clobazam (C₁₆H₁₃ClN₂O₂) in the portion of Clobazam taken:

Result = (r_u/r_s) × (C_s/C_u) × 100

r_u = peak response of clobazam from the Sample solution

r_s = peak response of clobazam from the Standard solution

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

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

Acceptance criteria: 97.0%–103.0% on the dried basis

4 IMPURITIES

4.1 Residue on Ignition 〈281〉: NMT 0.1%

4.2 Organic Impurities

4.2.1 Solution A, Solution B, Solution C, Diluent, and Chromatographic system: Proceed as directed in the Assay.

4.2.2 Mobile phase: See Table 2.

4.2.3 Sensitivity solution

0.25 μg/mL of USP Clobazam RS in Diluent

4.2.4 Standard stock solution

50 μg/mL each of USP Clobazam RS, USP Clobazam Related Compound A RS, USP Clobazam Related Compound E RS, and USP Clobazam Related Compound G RS in acetonitrile

4.2.5 Standard solution

0.5 μg/mL each of USP Clobazam RS, USP Clobazam Related Compound A RS, USP Clobazam Related Compound E RS, and USP Clobazam Related Compound G RS from the Standard stock solution in Diluent

4.2.6 Sample solution

500 μg/mL of Clobazam prepared as follows. Transfer a suitable amount of Clobazam to an appropriate volumetric flask and dissolve in 60% of the flask volume of acetonitrile. Dilute with water to volume.

4.2.7 System suitability

4.2.8 Samples

Sensitivity solution and Standard solution

[Note-See Table 3 for the relative retention times.]

4.2.9 Suitability requirements

Resolution: NLT 4.0 between clobazam related compound A and clobazam, Standard solution

Tailing factor: NMT 2.0 each for clobazam, clobazam related compound A, clobazam related compound E, and clobazam related compound G, Standard solution

Relative standard deviation: NMT 5.0% each for clobazam, clobazam related compound A, clobazam related compound E, and clobazam related compound G, Standard solution

Signal-to-noise ratio: NLT 10, Sensitivity solution

4.2.10 Analysis

4.2.10.1 Samples: Standard solution and Sample solution

Calculate the percentage of clobazam related compound A, clobazam related compound E, and clobazam related compound G in the portion of Clobazam taken:

Result = (r_u/r_s) × (C_s/C_u) × 100

r_u = peak response of clobazam related compound A, clobazam related compound E, or clobazam related compound G from the Sample solution

r_s = peak response of clobazam related compound A, clobazam related compound E, or clobazam related compound G from the Standard solution

C_s = concentration of USP Clobazam Related Compound A RS, USP Clobazam Related Compound E RS, or USP Clobazam Related Compound G RS in the Standard solution (μg/mL)

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

Calculate the percentage of any other speciffied and unspeciffied impurity in the portion of Clobazam taken:

Result = (r_u/r_s) × (C_s/C_u) × (1/F) × 100

r_u = peak response of any other specified or unspecified impurity from the Sample solution

r_s = peak response of clobazam from the Standard solution

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

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

F = relative response factor (see Table 3)

Acceptance criteria: See Table 3. The reporting threshold is 0.05%.

a: 1-Methyl-5-phenyl-1,5-dihydro-2H-benzo[b][1,4]diazepine-2,4(3H)-dione.

b:  7-Chloro-1,3-dimethyl-5-phenyl-1,5-dihydro-2H-benzo[b][1,4]diazepine-2,4(3H)-dione.

c: 7-Chloro-1,3,3-trimethyl-5-phenyl-1,5-dihydro-2H-benzo[b][1,4]diazepine-2,4(3H)-dione.

d: Methyl 3-{4-chloro-2-(phenylamino)phenylamino}-3-oxopropanoate.

e: Not including clobazam related compound A.

5 SPECIFIC TESTS

5.1 Loss on Drying 〈731〉

Analysis: Dry at 105° for 1 h.

Acceptance criteria: NMT 0.5%

6 ADDITIONAL REQUIREMENTS

6.1 Packaging and Storage

Store at controlled room temperature.

6.2 USP Reference Standards 〈11〉

USP Clobazam RS

USP Clobazam Related Compound A RS

8-Chloro-1-phenyl-1,5-dihydro-2H-benzo[b][1,4]diazepine-2,4(3H)-dione.

C₁₅H₁₁ClN₂O₂ 286.72

USP Clobazam Related Compound E RS

N-[4-chloro-2-(phenylamino)phenyl]-N-methylacetamide.

C₁₅H₁₅ClN₂O 274.75

USP Clobazam Related Compound G RS

6-Chloro-2,3-dimethyl-1-phenyl-1H-benzimidazol-3-ium chloride.

C₁₅H₁₄Cl₂N₂ 293.19 (USP 1-Dec-2023)