Clozapine Tablets

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

Clozapine Tablets contain NLT 90.0% and NMT 110.0% of the labeled amount of clozapine (C₁₈H₁₉CIN₄).

2 IDENTIFICATION

Change to read:

A. The UV spectrum of the major peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay. (USP 1-May-2021)

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

Change to read:

3.1 PROCEDURE

Mobile phase: Methanol (USP 1-May-2021) and water (80:20). To each liter add 0.75 mL of triethylamine. (USP 1-May-2021)

System suitability stock solution: Transfer 10 mg of clozapine to a suitable container, add 5 mL of 0.1 N hydrochloric acid VS. (USP 1-May-2021) and heat for 2 h at 90°. Transfer this solution to a 100-mL volumetric flask, add 15 mL of water, and dilute with methanol to volume.

Standard solution: 0.125 mg/mL of USP Clozapine RS prepared as follows. Transfer a suitable portion of USP Clozapine RS to an appropriate volumetric flask. (USP 1-May-2021) Dissolve in 80% of the flask volume of methanol. Dilute with water to volume. (USP 1-May-2021)

System suitability solution: System suitability stock solution and Standard solution (50:50) (USP 1-May-2021)

Sample solution: Nominally 0.125 mg/mL of clozapine from Tablets prepared as follows. Finely powder NLT 20 Tablets and transfer a portion of powder equivalent to 125 mg of clozapine to a 1-L volumetric flask. Dissolve in 640 mL of methanol, sonicate for 10 min, and dilute with water to volume. Pass the resulting solution through an appropriate filter and use the filtrate. (USP 1-May-2021)

Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 257 nm. For Identification A, use a diode array detector in the range of 210-400 nm.(USP 1-May-2021)

Column: 4.0-mm x 25-cm; 10-µm (USP 1-May-2021) packing LZ

Flow rate: 1 mL/min

Injection volume: (USP 1-May-2021) 10 µL

Run time: NLT 3 times the retention time of clozapine (USP 1-May-2021)

System suitability

Samples: Standard solution and System suitability solution

Suitability requirements

Resolution: NLT 1.5 between the clozapine peak and any other peak, System suitability solution

Column efficiency: NLT 1500 theoretical plates, Standard solution

Relative standard deviation: NMT 1.0% (USP 1-May-2021) for replicate injections, Standard solution

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of clozapine (CH₁,CIN) in the portion of Tablets taken:

Result = (r_u/r_s) × (C_s/C_u) × 100

r_u= peak response of clozapine (USP 1-May-2021) from the Sample solution

r_s = peak response of clozapine (USP 1-May-2021) from the Standard solution

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

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

Acceptance criteria: 90.0%-110.0%

4 PERFORMANCE TESTS

Change to read:

4.1 DISSOLUTION (711)

Medium: pH 4.0 acetate buffer (USP 1-May-2021) (Dissolve 2 g of sodium hydroxide in 450 mL of water. Adjust with glacial acetic acid to a pH of 4.0. Dilute with water (USP 1-May-2021) to 1 L.); 900 mL

Apparatus 1: 100 rpm

Time: 45 min

Standard solution:(L/900) mg/mL of USP Clozapine RS in Medium, where L is the label claim, in mg/Tablet. Dilute with Medium, if necessary. (USP 1-May-2021)

Sample solution: Pass a portion of the solution under test through a suitable filter. Dilute with Medium, if necessary.

Instrumental conditions

Mode: UV

Analytical wavelength: 290 nm

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of clozapine (C₁₈H₁₉CIN₄) dissolved:

Result = (A_u/A_s) x C_s x V x D x (1/L) x 100

A_u = absorbance of clozapine from the Sample solution

A_s = absorbance of clozapine from the Standard solution

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

V = volume of Medium, 900 mL

D = dilution factor, if needed

L = label claim (mg/Tablet) (USP 1-May-2021)

Tolerances: NLT 85% (Q) of the labeled amount of clozapine (C1H1CIN) is dissolved.

4.2 UNIFORMITY OF DOSAGE UNITS (905): Meet the requirements

5 IMPURITIES

Change to read:

5.1 ORGANIC IMPURITIES

Buffer: 2.0 g/L of monobasic potassium phosphate in water. Adjust with phosphoric acid to a pH of 2.4-2.5.

Solution A: Acetonitrile, methanol, and Buffer (10:10:80)

Solution B: Acetonitrile, methanol, and Buffer (40:40:20)

Mobile phase: See Table 1.

Table 1

Diluent: Methanol and water (80:20)

System suitability stock solution: 100 µg/mL of clozapine N-oxide prepared as follows. Transfer a suitable quantity of clozapine N-oxide to an appropriate volumetric flask. Dissolve in 80% of the flask volume of methanol. Dilute with water to volume.

System suitability solution: 750 µg/mL USP Clozapine Resolution Mixture RS and 0.75 µg/mL of clozapine N-oxide from System suitability stock solution prepared as follows. Transfer a suitable quantity of USP Clozapine Resolution Mixture RS to an appropriate volumetric flask. Dissolve in 80% of the flask volume of methanol. Add a suitable portion of System suitability stock solution. Dilute with water to volume.

Standard solution: 0.75 µg/mL of USP Clozapine RS in Diluent

Sensitivity solution: 0.38 µg/mL of USP Clozapine RS from Standard solution in Diluent

Sample stock solution: Nominally 3000 µg/mL of clozapine from Tablets prepared as follows. Finely powder NLT 10 Tablets. Transfer a suitable quantity of the powder to an appropriate volumetric flask. Dissolve in 80% of the flask volume of methanol, and sonicate for 10 min. Dilute with water to volume.

Sample solution: Nominally 750 µg/mL of clozapine from Sample stock solution prepared as follows. Transfer a suitable volume of Sample stock solution to an appropriate volumetric flask. Dissolve in Diluent. Centrifuge the resulting solution and use the supernatant. [NOTE-A centrifuge speed of 10,000 rpm for 10 min may be suitable.]

Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 257 nm

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

Column temperature: 35 ± 5°

Flow rate: 1 mL/min

Injection volume: 10 µL

System suitability

Samples: System suitability solution, Standard solution, and Sensitivity solution

[NOTE-The relative retention time for didiazepinyl Piperazine is 1.7. See Table 2 for the relative retention times.]

Suitability requirements

Resolution: NLT 1.5 between benzoyl methylpiperazine analog and clozapine N-oxide; NLT 1.5 between chlorodibenzodiazepinone and didiazepinyl piperazine, System suitability solution

Relative standard deviation: NMT 5.0% for clozapine, Standard solution

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

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of each related compound and any unknown impurity in the portion of Tablets taken:

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

r_u = peak response of any impurity from the Sample solution

r_s = peak response of clozapine from the Standard solution s

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

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

F = relative response factor of the impurity (see Table 2)

Acceptance criteria: See Table 2. The reporting threshold is 0.1%.

Table 2

a 8-Chloro-11-(piperazin-1-yl)-5H-dibenzo[b,e][1,4]diazepine.

b1-[2-[(2-Amino-4-chlorophenyl)amino]benzoyl]-4-methylpiperazine.

C4-(8-Chloro-5H-dibenzo[b,e][1,4]diazepin-11-yl)-1-methylpiperazine 1-oxide.

d 8-Chloro-5,10-dihydro-11H-dibenzo[b,e][1,4]diazepin-11-one.

(USP 1-May-2021)

6 ADDITIONAL REQUIREMENTS

Change to read:

6.1 PACKAGING AND STORAGE:

Preserve in well-closed containers. Store at controlled room temperature. (USP 1-May-2021)

Change to read:

6.2 USP REFERENCE STANDARDS (11)

USP Clozapine RS

USP Clozapine Resolution Mixture RS

Contains a mixture of the following 5 compounds:

Clozapine.

Chlorodibenzodiazepinone;

8-Chloro-5,10-dihydro-11H-dibenzo[b,e][1,4]diazepin-11-one.

C₁₃H1₈CIN₂O   244.68

Didiazepinyl piperazine;

1,4-Bis(8-chloro-5H-dibenzo[b,e][1,4]diazepin-11-yl)piperazine.

C₃₀H₂₄CI₂N₆   539.46

Demethyl clozapine;

8-Chloro-11-(piperazin-1-yl)-5H-dibenzo[b,e] [1,4]diazepine.

C₁₇H₁₇CIN₄   312.80

Benzoyl methylpiperazine analog;

1-[2-[(2-Amino-4-chlorophenyl)amino]benzoyl]-4-methylpiperazine.

C₁₈H₂₁CIN₄O    344.84

[NOTE-The contents have previously been referred to as clozapine, Impurity A, Impurity B, Impurity C, and Impurity D, respectively.] (USP 1-MAY-2021)