Acetazolamide Oral Suspension
Acetazolamide Oral Suspension contains NLT 90.0% and NMT 110.0% of the labeled amount of acetazolamide (C4H6N4O3S2).
Prepare Acetazolamide Oral Suspension, 25 mg/mL, as follows (see Pharmaceutical Compounding—Nonsterile Preparations 795; see also Acetazolamide Oral Solution).
Acetazolamide 2.5 g
Vehicle: a mixture of Vehicle for Oral Solution, NF (regular or sugar-free), and Vehicle for Oral Suspension, NF (1:1), or Cherry Syrup, NF, a sufficient quantity to make 100 mL
[Note—If tablets are used instead of bulk powder, the preparation becomes a suspension and should be labeled as such. ]
If using tablets, place in a mortar and comminute to a fine powder, or add Acetazolamide powder. Add about 20 mL of the Vehicle, and mix to a uniform paste. Add the Vehicle in small portions almost to volume, and mix thoroughly after each addition. Transfer the contents of the mortar, stepwise and quantitatively, to a calibrated bottle. Add enough liquid Vehicle to bring to final volume, and mix well.
•  Procedure
Mobile phase:  Dissolve 4.1 g of anhydrous sodium acetate in 950 mL of water, and add 20 mL of methanol and 30 mL of acetonitrile. Adjust with glacial acetic acid to a pH of 4.0.
Standard stock solution:  Transfer about 25 mg of USP Acetazolamide RS, accurately weighed, to a 50-mL volumetric flask, add 5.0 mL of 0.5 N sodium hydroxide, and mix to dissolve. Dilute with water to volume, and mix.
Standard solution:  250 µg/mL from the Standard stock solution in water
Sample solution:  250 µg/mL of acetazolamide from Oral Suspension in Mobile phase. Agitate the container of Oral Suspension for 30 min on a rotating mixer, remove a 5-mL sample, and store in a clear glass vial at 70 until analyzed. At the time of analysis, remove the sample from the freezer, allow to reach room temperature, and mix with a vortex mixer for 30 s. Pipet 1.0 mL of this solution to a 100-mL volumetric flask, and dilute with Mobile phase to volume.
Chromatographic system 
Mode:  LC
Detector:  UV 254 nm
Column:  4.6-mm × 25-cm; 5-µm packing L1
Flow rate:  2 mL/min
Injection size:  20 µL
System suitability 
Sample:  Standard solution
[Note—The retention time for the acetazolamide peak is about 3 min. ]
Suitability requirements 
Relative standard deviation:  NMT 1.1% for replicate injections
Samples:  Standard solution and Sample solution
Calculate the percentage of the labeled amount of acetazolamide (C4H6N4O3S2) in the portion of Oral Suspension taken:
Result = (rU/rS) × (CS/CU) × 100
rU== peak response from the Sample solution
rS== peak response from the Standard solution
CS== concentration of acetazolamide in the Standard solution (µg/mL)
CU== nominal concentration of acetazolamide in the Sample solution (µg/mL)
Acceptance criteria:  90.0%–110.0%
•  pH 791: 4.0–5.0 (Vehicle for Oral Solution and Vehicle for Oral Suspension), 3.1–3.9 (Cherry Syrup)
•  Packaging and Storage: Package in tight, light-resistant containers. Store at controlled room temperature, or in a cold place.
•  Labeling: Label it to state that it is to be well shaken before use, and to state the Beyond-Use Date.
•  Beyond-Use Date: NMT 60 days after the day on which it was compounded
•  USP Reference Standards 11
USP Acetazolamide RS Click to View Structure
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Jeanne H. Sun
Assistant Scientific Liaison
(CMP2010) Compounding
Reference Standards RS Technical Services
USP35–NF30 Page 2063
Pharmacopeial Forum: Volume No. 32(1) Page 44