Guanethidine Monosulfate Tablets, chemical structure, molecular formula, Reference Standards

Guanethidine Monosulfate Tablets

»Guanethidine Monosulfate Tablets contain an amount of guanethidine monosulfate (C10H22N4·H2SO4)equivalent to not less than 90.0percent and not more than 110.0percent of the labeled amount of guanethidine sulfate [(C10H22N4)2·H2SO4].

Packaging and storage— Preserve in well-closed containers.

USP Reference standards á11ñ— USP Guanethidine Monosulfate RS.

Identification,Infrared Absorption á197Mñ— Obtain the test specimen as follows.Transfer a quantity of powdered Tablets,equivalent to about 120mg of guanethidine monosulfate,to a glass-stoppered flask,add 20mLof water,shake by mechanical means for 30minutes,and filter,discarding the first few mLof the filtrate.Transfer 10mLof the filtrate to a separator,add 2mLof 0.1Nsodium hydroxide and 2mLof a saturated solution of picric acid in 0.1Nsodium hydroxide,and mix.Extract with 20mLof chloroform,filter the chloroform extract through cotton,and collect in a beaker.Evaporate the chloroform extract with the aid of a stream of nitrogen to dryness.

Dissolution á711ñ—

Medium: water;500mL.

Apparatus 1: 100rpm.

Time: 45minutes.

Procedure— Determine the amount of (C10H22N4)2·H2SO4dissolved,employing the procedure set forth in the Assayand making any necessary modifications.

Tolerances— Not less than 75%(Q)of the labeled amount of (C10H22N4)2·H2SO4is dissolved in 45minutes.

Uniformity of dosage units á905ñ: meet the requirements.

Assay—

Borate solution— Transfer 12.4g of boric acid to a 1000-mLvolumetric flask,dissolve in 100mLof 1.0Nsodium hydroxide,dilute with water to volume,and mix.

Borate buffer— Mix 400mLof Borate solutionwith 600mLof 0.1Nsodium hydroxide,and adjust with 1.0Nsodium hydroxide or 1.0Nhydrochloric acid to a pHof 12.3±0.1.

Picrate reagent— Transfer 15g of picric acid to a 1000-mLvolumetric flask,dissolve in 750mLof 0.1Nsodium hydroxide,dilute with water to volume,and mix.

Standard preparation— Prepare a solution in 0.1Nsulfuric acid having a known concentration of about 0.3mg of USP Guanethidine Monosulfate RSper mL.

Assay preparation— Finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 50mg of guanethidine sulfate,to a 200-mLvolumetric flask,add 150mLof 0.1Nsulfuric acid,shake by mechanical means for 30minutes,dilute with 0.1Nsulfuric acid to volume,and mix.Filter,and discard the first 25mLof the filtrate.

Procedure— Pipet 5mLeach of the Standard preparationand the Assay preparationinto separate 125-mLseparators.To each separator add 20mLof Borate bufferand 20mLof Picrate reagent.Extract with three 20-mLportions of chloroform,filtering the extracts through chloroform-prerinsed cotton,and collect the extracts in low-actinic 100-mLvolumetric flasks.Rinse the cotton with 20mLof chloroform,adding the rinsings to the volumetric flasks,dilute with chloroform to volume,and mix.Concomitantly determine the absorbances of the solutions at the wavelength of maximum absorbance at about 412nm,with a suitable spectrophotometer,using chloroform as the blank.Calculate the quantity,in mg,of guanethidine sulfate [(C10H22N4)2·H2SO4]in the portion of Tablets taken by the formula:

(247.35/296.39)(200)(C)(AU/AS),

in which 247.35is one-half the molecular weight of guanethidine sulfate,296.39is the molecular weight of guanethidine monosulfate,Cis the concentration,in mg per mL,of USP Guanethidine Monosulfate RSin the Standard preparation,and AUand ASare the absorbances of the solutions from the Assay preparationand the Standard preparation,respectively.

Auxiliary Information— Staff Liaison:Andrzej Wilk,Ph.D.,Senior Scientific Associate

Expert Committee:(PA5)Pharmaceutical Analysis 5

USP28–NF23Page 932

Phone Number:1-301-816-8305