Quinidine Sulfate Oral Suspension
Quinidine Sulfate Oral Suspension contains NLT 90.0% and NMT 110.0% of the labeled amount of quinidine sulfate [(C20H24N2O2)2·H2SO4·2H2O]. Prepare Quinidine Sulfate Oral Suspension 10 mg/mL as follows (see Pharmaceutical Compounding—Nonsterile Preparations 795).
Quinidine Sulfate 1 g
Vehicle: a mixture of Vehicle for Oral Solution (regular or sugar-free), NF, and Vehicle for Oral Suspension, NF (1:1), a sufficient quantity to make 100 mL
If using Quinidine Sulfate Tablets, place in a suitable mortar, and comminute into a fine powder, or add Quinidine Sulfate powder to the mortar. Add 15 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 to the calibrated bottle. Add sufficient Vehicle to volume, and mix well.
•  Procedure
Solution A:  Add 35.0 mL of methanesulfonic acid to 20.0 mL of glacial acetic acid, and dilute with water to 500 mL.
Solution B:  Dissolve 10.0 mL of diethylamine in water to obtain 100 mL of solution.
Mobile phase:  Acetonitrile, Solution A, Solution B, and water (10:1:1:40)
Standard solution:  100 µg/mL of USP Quinidine Sulfate RS, in Mobile phase
Sample solution:  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 it to reach room temperature, and mix on a vortex mixer for 30 s. Pipet 1.0 mL of the Sample solution into a 100-mL volumetric flask, and dilute with Mobile phase to volume.
Chromatographic system  
Mode:  LC
Detector:  UV 235 nm
Column:  4.6-mm × 25-cm; 5-µm packing L1
Flow rate:  1 mL/min
Injection size:  20 µL
System suitability 
Sample:  Standard solution
[Note—The retention time for quinidine sulfate is about 8.5 min. ]
Suitability requirements 
Relative standard deviation:  NMT 1.0%
Samples:  Standard solution and Sample solution
Calculate the percentage of (C20H24N2O2)2·H2SO4·2H2O in the volume of Oral Suspension taken:
Result = 100 × (C/V) × (rb,U + rd,U)/(rb,S + rd,S)
C== concentration of USP Quinidine Sulfate RS in the Standard solution (mg/mL)
V== volume of Oral Suspension taken (mL)
rb,U== peak response of quinidine from the Sample solution
rd,U== peak response of dihydroquinidine from the Sample solution
rb,S== peak response of quinidine from the Standard solution
rd,S== peak response of dihydroquinidine from the Standard solution
Acceptance criteria:  90.0%–110.0%
•  pH 791: 3.4–4.4
•  Packaging and Storage: Preserve in tight, light-resistant containers. Store at room temperature, or in a cold place.
•  Beyond-Use Date: 60 days after the day on which it was compounded
•  Labeling: Label it to state that it is to be well shaken before use, and to state the beyond-use date.
•  USP Reference Standards 11
USP Quinidine Sulfate 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 4506
Pharmacopeial Forum: Volume No. 35(6) Page 1475