Guanabenz Acetate 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

Change to read:

Guanabenz Acetate Tablets contain an amount of guanabenz acetate equivalent to (USP 1-May-2019) NLT 90.0% and NMT 110.0% of the labeled amount of guanabenz (C₈H₈N₄Cl₂).

2 IDENTIFICATION

A.

Sample: Transfer an amount of powdered Tablets, equivalent to 8 mg of guanabenz, to a 60-mL separator. Add 10 mL of 0.1 N hydrochloric acid, and shake to disperse the powder. Shake the mixture with three 10-mL portions of chloroform, discarding the chloroform phase each time. Add 5 mL of 1 N sodium hydroxide, and extract with two 25-mL portions of ether, filtering the ether extracts. Evaporate the combined extracts to dryness with the aid of a current of air.

Acceptance criteria: The IR absorption spectrum of a potassium bromide dispersion of the Sample exhibits maxima at the same wavelengths as those of a similar preparation of USP Guanabenz Acetate RS.

Add the following:

B. The retention time of the major peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay. (USP 1-May-2019)

3 ASSAY

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3.1 Procedure

Mobile phase: Methanol, phosphoric acid, and water (430:3:570)

Diluent: Dissolve 8.2 g of sodium acetate in 20 mL of water, add 5.7 mL of glacial acetic acid, and dilute with methanol to 1 L.

System suitability solution: Transfer 30 mg of guanabenz acetate to a 100-mL stoppered flask. Add about 50 mL of 0.1 N hydrochloric acid, heat on a steam bath for 60 min, and allow the solution to cool.

Standard solution: 0.1 mg/mL of USP Guanabenz Acetate RS in Diluent prepared as follows. Transfer a suitable amount of USP Guanabenz Acetate RS to a suitable volumetric flask. Add 10% of the total volume of water, shake to dissolve the solids, and dilute with Diluent to volume.

Sample solution: Nominally 0.08 mg/mL of guanabenz prepared as follows. Transfer 10 Tablets to a 500-mL volumetric flask. Add 50 mL of water, stir by mechanical means until the solids are well dispersed, add 400 mL of Diluent, and stir for 45 min. Dilute with Diluent to volume, and centrifuge a portion of the mixture until a clear supernatant is obtained. If necessary, dilute a portion of the supernatant quantitatively with a mixture of Diluent and water (90:10).

3.2 Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 245 nm

Column: 3.9-mm (USP 1-May-2019) × 30-cm; 10-μm (USP 1-May-2019) packing L1

Flow rate: 2 mL/min

Injection volume: 20 μL

Run time: NLT 6 times the retention time of the guanabenz peak (USP 1-May-2019)

3.3 System suitability

Samples: System suitability solution and Standard solution

3.4 Suitability requirements

Resolution: NLT 1.6 between guanabenz and the peak eluting before it, System suitability solution

Relative standard deviation: NMT 2.0%, Standard solution

3.5 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of guanabenz (C₈H₈N₄Cl₂) in the portion of Tablets taken:

Result = (r_U/r_S) × (C_S/C_U) × (M_r1/M_r2) × 100

r_U = peak response from the Sample solution

r_S = peak response from the Standard solution

C_S = concentration of USP Guanabenz Acetate RS in the Standard solution (mg/mL)

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

M_r1 = molecular weight of guanabenz, 231.08

M_r2 = molecular weight of guanabenz acetate, 291.13

Acceptance criteria: 90.0%–110.0%

4 PERFORMANCE TESTS

Dissolution 〈711〉

Medium: Water; 1000 mL

Apparatus 2: 50 rpm

Time: 60 min

Standard solution: A known concentration of USP Guanabenz Acetate RS in Medium

Sample solution: Pass a portion of the solution under test through a suitable filter, and dilute with Medium to a concentration similar to that of the Standard solution.

Instrumental conditions

Mode: UV-Vis

Analytical wavelength: Maximum absorbance at about 272 nm

Analysis

Samples: Standard solution and Sample solution

Determine the percentage of the labeled amount of guanabenz (C₈H₈N₄Cl₂) dissolved.

Tolerances: NLT 75% (Q) of the labeled amount of guanabenz (C₈H₈N₄Cl₂) is dissolved.

Uniformity of Dosage Units 〈905〉: Meet the requirements

5 IMPURITIES

Organic Impurities

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

Standard solution: Dilute 2 mL of the Standard solution from the Assay with Diluent to 100 mL.

Analysis

Samples: Sample solution and Standard solution

Calculate the percentage of any impurity observed having a relative retention time corresponding to the component eluting before guanabenz from the System suitability solution.

Acceptance criteria: NMT 2%

6 ADDITIONAL REQUIREMENTS

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

USP Reference Standards 〈11〉

USP Guanabenz Acetate RS