Acetazolamide

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

DOWNLOAD PDF HERE

C₄H₆N₄O₃S₂  222.24  (USP 1-May-2024)

Acetamide, N-[5-(aminosulfonyl)-1,3,4-thiadiazol-2-yl]-;

N-(5-Sulfamoyl-1,3,4-thiadiazol-2-yl)acetamide CAS RN®: 59-66-5; UNII: O3FX965V0I.

1 DEFINITION

Acetazolamide contains NLT 98.0% and NMT 102.0% of acetazolamide (C H N O S ), calculated on the anhydrous basis.

2 IDENTIFICATION

Change to read:

A. Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197A or  (USP 1-May-2024) 197K

B. The retention time of the major peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay.

3 ASSAY

Change to read:

3.1 Procedure

Mobile phase: Dissolve 4.1 g of anhydrous sodium acetate in 950 mL of water. Add 20 mL of methanol and 30 mL of acetonitrile, and mix. Adjust with glacial acetic acid to a pH of 4.0.

Standard solution: 0.1 mg/mL of USP Acetazolamide RS prepared as follows. Transfer an appropriate amount of USP Acetazolamide RS into a suitable volumetric flask, add 0.5 N sodium hydroxide equivalent to 10% of the flask volume, and dilute with water to volume.

Sample solution: 0.1 mg/mL of Acetazolamide prepared as follows. Transfer an appropriate amount of Acetazolamide into a suitable volumetric flask, add 0.5 N sodium hydroxide equivalent to 10% of the flask volume, and dilute with water to volume.

3.2 Chromatographic system

Mode: LC

Detector: UV 254 nm

Column: 4.6-mm × 25-cm; 5-μm (USP 1-May-2024) packing L1

Flow rate: 2 mL/min

Injection volume: 20 μL

Run time: NLT 1.5 times the retention time of acetazolamide (USP 1-May-2024)

3.3 System suitability

Sample: Standard solution

3.4 Suitability requirements

Tailing factor: NMT 1.5

Relative standard deviation: NMT 0.73%

3.5 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of acetazolamide (C₄H₆N₄O₃S₂) in the portion of Acetazolamide taken:

Result = (r_u/r_s) × (C_s/C_u) × 100

r_u = peak response of acetazolamide from the Sample solution

r_s = peak response of acetazolamide from the Standard solution

C_s = concentration of USP Acetazolamide RS in the Standard solution (mg/mL)

C_u = concentration of Acetazolamide in the Sample solution (mg/mL)

Acceptance criteria: 98.0%–102.0% on the anhydrous basis

4 IMPURITIES

Residue on Ignition 〈281〉: NMT 0.1%

Chloride and Sulfate 〈221〉, Chloride

Sample solution: Digest 1.5 g with 75 mL of water at about 70° for 5 min. Cool to room temperature, and lter.

Acceptance criteria: A 25-mL portion of the ltrate shows no more chloride than corresponds to 0.10 mL of 0.020 N hydrochloric acid (0.014%).

Chloride and Sulfate 〈221〉, Sulfate

Sample solution: A 25-mL portion of the ltrate prepared in the test for Chloride and Sulfate, Chloride

Acceptance criteria: It shows no more sulfate than corresponds to 0.20 mL of 0.020 N sulfuric acid (0.04%).

Change to read:

4.1 Organic Impurities

Solution A: 13.61 g/L of monobasic potassium phosphate in water

Mobile phase: Methanol and Solution A (10:90)

Standard stock solution: 0.4 mg/mL of USP Acetazolamide RS in Mobile phase prepared as follows. Transfer an appropriate amount of USP Acetazolamide RS to a suitable volumetric flask. Add 20% of the flask volume of methanol, and sonicate for 15 min with occasional shaking to dissolve. Dilute with Mobile phase to volume.

Standard solution: 0.005 mg/mL of USP Acetazolamide RS from Standard stock solution in Mobile phase

Sensitivity solution: 0.5 μg/mL  (USP 1-May-2024) of USP Acetazolamide RS from Standard solution in Mobile phase

Sample solution: 1 mg/mL of Acetazolamide in Mobile phase prepared as follows. Transfer an appropriate amount of Acetazolamide to asuitable volumetric flask. Add 20% of the flask volume of methanol, and sonicate for 15 min with occasional shaking to dissolve. Dilute with Mobile phase to volume.

4.2 Chromatographic system

Mode: LC

Detector: UV 254 nm

Column: 4.6-mm × 15-cm; 3.5-μm packing L10

Column temperature: 30°

Flow rate: 1.0 mL/min

Injection volume: 30 μL

Run time: NLT 9.5 times the retention time of acetazolamide

4.3 System suitability

Samples: Standard solution and Sensitivity solution

[Note - The relative retention times in Table 1 are provided as information that could aid in peak assignment.]

Table 1 (USP 1-May-2024)

^a 5-Amino-1,3,4-thiadiazole-2-sulfonamide.

^b 5-Acetamido-1,3,4-thiadiazole-2-sulfonic acid.

^c N-(1,3,4-Thiadiazol-2-yl)acetamide.

^d N-(5-Mercapto-1,3,4-thiadiazol-2-yl)acetamide.

^e N-(5-Chloro-1,3,4-thiadiazol-2-yl)acetamide.

^f N,N′-{5,5′-[(Hydrosulfonylamino)sulfonyl]bis(1,3,4-thiadiazole-5,2-diyl)}diacetamide.

4.4 Suitability requirements

Tailing factor: NMT 2.0, Standard solution

Relative standard deviation: NMT 5.0%, Standard solution

Signal-to-noise ratio: NLT 14, Sensitivity solution

4.5 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of each impurity in the portion of Acetazolamide taken:

Result = (r_u/r_s) × (C_s/C_u) × (1/F) × 100

r_u= peak area of each impurity from the Sample solution

r_s = peak area of acetazolamide from the Standard solution

C_s= concentration of USP Acetazolamide RS in the Standard solution (mg/mL)

C_u = concentration of Acetazolamide in the Sample solution (mg/mL)

F = relative response factor (see Table 2)

Acceptance criteria: See Table 2.The reporting threshold is 0.05%. (USP 1-May-2024)

Table 2

5 SPECIFIC TESTS

Water Determination 〈921〉, Method I: NMT 0.5%

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight containers. Store at room temperature.