Azathioprine Oral Suspension
DEFINITION
Azathioprine Oral Suspension contains NLT 90.0% and NMT 110.0% of the labeled amount of azathioprine (C9H7N7O2S).
Prepare Azathioprine Oral Suspension of 50 mg/mL as follows (see Pharmaceutical Compounding—Nonsterile Preparations 
795
).
795).| Azathioprine | 5 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 tablets, comminute them to a fine powder in a suitable mortar, or add Azathioprine powder to the mortar. Add about 10 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 sufficient Vehicle to bring to final volume, and mix well.
[Caution—Avoid skin contact or inhalation of azathioprine by using protective gloves and a fume hood or surgical mask.
]
ASSAY
• Procedure
Mobile phase:
Dissolve 1.1 g of sodium-1-heptanesulfonate in 700 mL of water, and add 300 mL of methanol. Adjust with 1 N hydrochloric acid to a pH of 3.5.
Standard solution:
25 mg of USP Azathioprine RS, in a 50-mL volumetric flask. Add 15 mL of methanol and 0.5 mL of ammonium hydroxide to the flask, swirl, and sonicate for 2 min. Dilute with methanol to volume. Transfer 10 mL of this solution to a 50-mL volumetric flask, and dilute with water to volume.
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 with a vortex mixer for 30 s. Pipet 1.0 mL of the Sample into a 100-mL volumetric flask, and dilute with Mobile phase to volume.
70 until analyzed. At the time of analysis, remove the sample from the freezer, allow it to reach room temperature, and mix with a vortex mixer for 30 s. Pipet 1.0 mL of the Sample into 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 azathioprine peak is about 4 min. ]
Suitability requirements
Relative standard deviation:
NMT 1.3% for replicate injections
Analysis
Samples:
Standard solution and Sample solution
Calculate the percentage of the labeled amount of azathioprine (C9H7N7O2S) 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 azathioprine in the Standard solution (µg/mL) |
| CU | = | = nominal concentration of azathioprine in the Sample solution (µg/mL) |
Acceptance criteria:
90.0%–110.0%
SPECIFIC TESTS
• pH 791:
3.8–4.8
791:
3.8–4.8
ADDITIONAL REQUIREMENTS
• Packaging and Storage:
Package in tight, light-resistant containers. Store at 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
11
USP Azathioprine RS 
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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 1-301-816-3361 |
(CMP2010) Compounding |
| Reference Standards | RS Technical Services 1-301-816-8129 rstech@usp.org |
USP35–NF30 Page 2277
Pharmacopeial Forum: Volume No. 32(1) Page 48