Guanethidine Monosulfate

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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C₁₀H₂₂N₄ · H₂SO₄ 296.39

Guanidine, [2-(hexahydro-1(2H)-azocinyl)ethyl]-, sulfate (1:1);

[2-(Hexahydro-1(2H)-azocinyl)ethyl]guanidine sulfate (1:1) CAS RN®: 645-43-2; UNII: 5UBY8Y002G.

1 DEFINITION

Guanethidine Monosulfate contains NLT 97.0% and NMT 103.0% of guanethidine monosulfate (C₁₀H₂₂N₄ · H₂SO₄), calculated on the dried basis.

2 IDENTIFICATION

Change to read:

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

B.

Sample solution: 2.5 mg dissolved in 10 mL of water

Analysis: To the Sample solution add 2 mL of a solution prepared by dissolving 500 mg of 1-naphthol, 3 g of sodium hydroxide, and 8 g of sodium carbonate in water to make 50 mL, and 1 mL of a solution of 2,3-butanedione (1 in 2000). Allow to stand at room temperature.

Acceptance criteria: An intense, pinkish-red color develops.

3 ASSAY

3.1 Procedure

Solution A: 10 mg/mL of sodium nitroferricyanide and 10 mg/mL of potassium ferricyanide in water

Standard solution: 1 mg/mL of USP Guanethidine Monosulfate RS in 1 N sulfuric acid

Sample solution: 1 mg/mL of Guanethidine Monosulfate in 1 N sulfuric acid

Blank: 1 N sulfuric acid

3.2 Instrumental conditions

Mode: UV-Vis

Analytical wavelength: Maximum absorbance at about 500 nm

Cell: 1 cm

3.3 Analysis

Samples: Standard solution, Sample solution, and Blank Pipet 2 mL each of the Standard solution, Sample solution, and Blank into separate glass-stoppered, 40-mL centrifuge tubes. Add 10.0 mL of water to each tube. Add 10.0 mL of Solution A, and mix. Add 4.0 mL of 1 N sodium hydroxide to each tube, mix, and allow to stand for 20 min, accurately timed.

Calculate the percentage of guanethidine monosulfate (C₁₀H₂₂N₄ · H₂SO₄) in the portion of Guanethidine Monosulfate taken:

Result = (A_U/A_S) × (C_S/C_U) × 100

A_U = absorbance of the Sample solution

A_S = absorbance of the Standard solution

C_S = concentration of USP Guanethidine Monosulfate RS in the Standard solution (mg/mL)

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

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

4 IMPURITIES

Residue on Ignition 〈281〉: NMT 0.2%

5 SPECIFIC TESTS

Loss on Drying 〈731〉

Analysis: Dry at 105° to constant weight.

Acceptance criteria: NMT 0.5%

pH 〈791〉

Sample solution: 20 mg/mL

Acceptance criteria: 4.7–5.7

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in well-closed containers.

USP Reference Standards 〈11〉

USP Guanethidine Monosulfate RS