(a seet'' a zol' a mide).
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C4H6N4O3S2 222.25

Acetamide, N-[5-(aminosulfonyl)-1,3,4-thiadiazol-2-yl]-.
N-(5-Sulfamoyl-1,3,4-thiadiazol-2-yl)acetamide [59-66-5].
» Acetazolamide contains not less than 98.0 percent and not more than 102.0 percent of C4H6N4O3S2, calculated on the anhydrous basis.
Packaging and storage— Preserve in tight containers, and store at room temperature.
USP Reference standards 11
USP Acetazolamide RS Click to View Structure
B: Dissolve about 100 mg in 5 mL of 1 N sodium hydroxide. Add 5 mL of a solution made by dissolving 100 mg of hydroxylamine hydrochloride and 80 mg of cupric sulfate in 10 mL of water. Mix, and heat the resulting pale yellow solution on a steam bath for 5 minutes: a clear, bright yellow solution is produced. No heavy precipitate or dark brown color results after the mixing or heating.
Water, Method I 921: not more than 0.5%.
Residue on ignition 281: not more than 0.1%.
Chloride 221 Digest 1.5 g with 75 mL of water at about 70 for 5 minutes. Cool to room temperature, and filter: a 25-mL portion of the filtrate shows no more chloride than corresponds to 0.10 mL of 0.020 N hydrochloric acid (0.014%).
Sulfate 221 A 25-mL portion of the filtrate prepared in the test for Chloride shows no more sulfate than corresponds to 0.20 mL of 0.020 N sulfuric acid (0.04%).
Selenium 291: 0.003%, a 200-mg specimen being used.
Silver-reducing substances— Thoroughly wet 5.0 g with alcohol. Add 125 mL of water, 10 mL of nitric acid, and 5.0 mL of 0.1 N silver nitrate VS. Stir with a mechanical stirrer for 30 minutes. Filter, add 5 mL of ferric ammonium sulfate TS to the filtrate, and titrate with 0.1 N ammonium thiocyanate VS to a reddish-brown endpoint: not less than 4.8 mL of 0.1 N ammonium thiocyanate is required.
Ordinary impurities 466
Test solution: a mixture of acetone and methanol (1:1).
Standard solution: a mixture of acetone and methanol (1:1).
Eluant: a mixture of n-propyl alcohol and 1 N ammonium hydroxide (88:12).
Visualization: 1.
Assay— Dissolve about 200 mg of Acetazolamide, accurately weighed, in a small volume of pyridine in a 10-mL volumetric flask, add the solvent to volume, and mix. Similarly, dissolve an accurately weighed quantity of USP Acetazolamide RS in pyridine to obtain a Standard solution having a known concentration of about 20 mg per mL. Concomitantly determine the absorbances of both solutions in 0.1-mm cells at the wavelength of maximum absorbance at about 7.38 µm (1350 cm1), with a suitable IR spectrophotometer, using pyridine as the blank. Calculate the quantity, in mg, of C4H6N4O3S2 in the portion of Acetazolamide taken by the formula:
10C(AU / AS)
in which C is the concentration, in mg per mL, of USP Acetazolamide RS in the Standard solution; and AU and AS are the absorbances of the solution of Acetazolamide and the Standard solution, respectively.
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Topic/Question Contact Expert Committee
Monograph Feiwen Mao, M.S.
Senior Scientific Liaison
(SM32010) Monographs - Small Molecules 3
Reference Standards RS Technical Services
USP35–NF30 Page 2062
Pharmacopeial Forum: Volume No. 27(3) Page 2500