Guanethidine Monosulfate
(gwahn eth' i deen mon'' oh sul' fate).
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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) [645-43-2].
» Guanethidine Monosulfate contains not less than 97.0 percent and not more than 103.0 percent of C10H22N4·H2SO4, calculated on the dried basis.
Packaging and storage— Preserve in well-closed containers.
USP Reference standards 11
USP Guanethidine Monosulfate RS Click to View Structure
B: Dissolve 2.5 mg in 10 mL of water. 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: an intense, pinkish-red color develops.
pH 791: between 4.7 and 5.7, in a solution containing 20 mg per mL.
Loss on drying 731 Dry it at 105 to constant weight: it loses not more than 0.5% of its weight.
Residue on ignition 281: not more than 0.2%.
Sodium nitroferricyanide–potassium ferricyanide solution— Dissolve 1 g of sodium nitroferricyanide and 1 g of potassium ferricyanide in water to make 100 mL, and mix.
Standard preparation— Dissolve a suitable quantity of USP Guanethidine Monosulfate RS, accurately weighed, in 1 N sulfuric acid to obtain a solution having a known concentration of about 1 mg per mL.
Assay preparation— Transfer about 50 mg of Guanethidine Monosulfate, accurately weighed, to a 50-mL volumetric flask, dissolve in 1 N sulfuric acid, add 1 N sulfuric acid to volume, and mix.
Procedure— Pipet 2 mL each of the Assay preparation and the Standard preparation, and 2 mL of 1 N sulfuric acid to provide the blank, into separate glass-stoppered, 40-mL centrifuge tubes. Add 10.0 mL of water to each tube, and mix. To each tube add 10.0 mL of Sodium nitroferricyanide–potassium ferricyanide solution, mix, add 4.0 mL of 1 N sodium hydroxide, mix, and allow to stand for 20 minutes, accurately timed. Concomitantly determine the absorbances of both solutions in 1-cm cells against the blank at the wavelength of maximum absorbance at about 500 nm, with a suitable spectrophotometer. Calculate the quantity, in mg, of C10H22N4·H2SO4 in the Guanethidine Monosulfate taken by the formula:
50C(AU / AS)
in which C is the concentration, in mg per mL, of USP Guanethidine Monosulfate RS in the Standard preparation; and AU and AS are the absorbances of the solutions from the Assay preparation and the Standard preparation, respectively.
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Monograph Sujatha Ramakrishna, Ph.D.
Senior Scientific Liaison
(SM22010) Monographs - Small Molecules 2
Reference Standards RS Technical Services
USP35–NF30 Page 3389