Mercaptopurine Tablets
The retention time of the major peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay.USP35
Solution A:
0.77 g/L of ammonium acetate in water
711
Organic Impurities
USP35
DEFINITION
Mercaptopurine Tablets contain NLT 93.0% and NMT 110.0% of the labeled amount of mercaptopurine (C5H4N4S·H2O).
IDENTIFICATION
Change to read:
• A.
The UV absorption spectrum exhibits a maximum at 325 ± 2 nm, and the ratio A255/A325 does not exceed 0.09.
Sample:
5 µg/mL of mercaptopurine in a mixture of methanol and water (1:1), from the Sample solution in the AssayUSP35
5 µg/mL of mercaptopurine in a mixture of methanol and water (1:1), from the Sample solution in the AssayUSP35
Change to read:
• B.
The retention time of the major peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay.USP35
ASSAY
Change to read:
• Procedure
Solution A:
0.77 g/L of ammonium acetate in water
Solution B:
Methanol and Solution A (5:95)
Solution C:
Methanol and Solution A (30:70)
Mobile phase:
Solution B and Solution C (80:20)
Diluent:
Methanol and water (1:1)
Standard solution:
0.25 mg/mL of USP Mercaptopurine RS in a mixture of methanol and water (1:1). Transfer USP Mercaptopurine RS into a suitable volumetric flask, and add methanol equivalent to 50% of the final volume. Shake mechanically to dissolve, and dilute with water to volume.
Sample stock solution:
0.5 mg/mL of mercaptopurine in Diluent from NLT 5 Tablets. Place the Tablets into a suitable volumetric flask, add methanol equivalent to 50% of the final volume, and shake mechanically for a minimum of 30 min. Dilute with water to volume. Pass through a PVDF filter of 0.45-µm pore size, and discard the first 3 mL of filtrate.
Sample solution:
0.25 mg/mL of mercaptopurine in Diluent from the Sample stock solution
Chromatographic system
Mode:
LC
Detector:
UV 260 nm
Column:
4.6-mm × 10-cm; 3-µm packing L1
Column temperature:
30
Flow rate:
1.0 mL/min
Injection size:
10 µL
System suitability
Sample:
Standard solution
Suitability requirements
Tailing factor:
NMT 2.0
Relative standard deviation:
NMT 2.0%
Analysis
USP35
Samples:
Standard solution and Sample solution
Calculate the percentage of mercaptopurine (C5H4N4S·H2O) in the portion of Tablets taken:
Result = (rU/rS) × (CS/CU) × (Mr1/Mr2) × 100
| rU | = | = peak response from the Sample solution |
| rS | = | = peak response from the Standard solution |
| CS | = | = concentration of USP Mercaptopurine RS in the Standard solution (mg/mL) |
| CU | = | = nominal concentration of mercaptopurine in the Sample solution (mg/mL) |
| Mr1 | = | = molecular weight of mercaptopurine, 170.19 |
| Mr2 | = | = molecular weight of anhydrous mercaptopurine, 152.18 |
USP35
Acceptance criteria:
93.0%–110.0%
PERFORMANCE TESTS
Change to read:
• Dissolution 711
Test 1
Medium:
0.1 N hydrochloric acid; 900 mL
Apparatus 2:
50 rpm
Time:
60 min
Mobile phase:
0.1% acetic acid in water
Standard solution:
USP Mercaptopurine RS in Medium
Sample solution:
Pass a portion of the solution under test through a suitable filter. Dilute with Medium to a concentration that is similar to the Standard solution, if necessary.
Chromatographic system
Mode:
LC
Detector:
UV 230 nm
Column:
3.9-mm × 15-cm; packing L1
Flow rate:
2.5 mL/min
Injection size:
10 µL
System suitability
Sample:
Standard solution
[Note—The retention time for mercaptopurine is NLT 4 min. ]
Suitability requirements
Relative standard deviation:
NMT 2.0%
Analysis
Samples:
Standard solution and Sample solution
Tolerances:
NLT 80% (Q) of the labeled amount of C5H4N4S·H2OUSP35 is dissolved.
H2OUSP35 is dissolved.
Test 2:
If the product complies with this test, the labeling indicates that it meets USP Dissolution Test 2.
Medium, Apparatus 2, Chromatographic system, and Analysis:
Proceed as directed for Test 1.
Time:
120 min
Tolerances
NLT 80% (Q) of the labeled amount of C5H4N4S·H2O is dissolved.
• Uniformity of Dosage Units 905:
Meets the requirements
905:
Meets the requirements
IMPURITIES
Add the following:
Organic Impurities
• Procedure
Solution A:
0.1% (v/v) formic acid in water
Solution B:
Methanol and Solution A (2:98)
Solution C:
Methanol and Solution A (1:1)
Mobile phase:
See Table 1.
Table 1
| Time (min) |
Solution B (%) |
Solution C (%) |
|---|---|---|
| 0 | 100 | 0 |
| 8 | 100 | 0 |
| 20 | 0 | 100 |
| 25 | 0 | 100 |
| 27 | 100 | 0 |
| 30 | 100 | 0 |
Standard stock solution:
0.06 mg/mL of USP Mercaptopurine RS in Solution A. [Note—Use methanol equivalent to 2.5% of the final volume to help dissolve. ]
Standard solution:
1.2 µg/mL of USP Mercaptopurine RS in Solution B from the Standard stock solution
Sensitivity solution:
0.06 µg/mL of USP Mercaptopurine RS in Solution B from the Standard solution
Sample stock solution:
0.5 mg/mL of mercaptopurine in a mixture of methanol and Solution A (1:9) from NLT 5 Tablets. Place the Tablets into a suitable volumetric flask, add methanol equivalent to 10% of the final volume, and shake mechanically for a minimum of 30 min. Dilute with water to volume. Pass through a PVDF filter of 0.45-µm pore size, and discard the first 3 mL of filtrate.
Sample solution:
0.12 mg/mL of mercaptopurine in Solution A. Transfer 6.0 mL of the Sample stock solution into a 25-mL volumetric flask, and dilute with Solution A to volume. Pass through a PVDF filter of 0.45-µm pore size, and discard the first 5 mL of filtrate. [Note—Inject the Sample solution within 1 h of preparation. ]
Chromatographic system
Mode:
LC
Detector:
UV 260 nm
Column:
4.6-mm × 10-cm; 3-µm packing L1
Temperature
Column:
30
Sample:
4
Flow rate:
1.0 mL/min
Injection size:
50 µL
System suitability
Samples:
Standard solution and Sensitivity solution
Suitability requirements
Tailing factor:
NMT 2.0, Standard solution
Signal-to-noise ratio:
NLT 10, Sensitivity solution
Relative standard deviation:
NMT 2.0%, Standard solution
Analysis
Samples:
Standard solution and Sample solution
Calculate the percentage of each impurity in the portion of Tablets taken:
Result = (rU/rS) × (CS/CU) × (1/F) × 100
| rU | = | = peak response of each impurity from the Sample solution |
| rS | = | = peak response of mercaptopurine from the Standard solution |
| CS | = | = concentration of USP Mercaptopurine RS in the Standard solution (mg/mL) |
| CU | = | = nominal concentration of mercaptopurine in the Sample solution (mg/mL) |
| F | = | = relative response factor for each individual impurity (see Table 2) |
Acceptance criteria
Individual impurities:
See Table 2. [Note—Disregard any impurity peak less than 0.05%. ]
Table 2
| Name | Relative Retention Time |
Relative Response Factor |
Acceptance Criteria, NMT (%) |
|---|---|---|---|
| Didanosine related compound Aa | 0.54 | 6.3 | 0.3 |
| Mercaptopurine | 1.00 | — | — |
| Mercaptopurine disulfideb | 2.90 | 4.4 | 0.4 |
| Any unspecified impurity |
— | 1.0 | 0.2 |
| Total impurities | — | — | 0.6 |
|
a
Hypoxanthine.
b
1,2-Di(9H-purin-6-yl)disulfane.
|
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USP35ADDITIONAL REQUIREMENTS
• Packaging and Storage:
Preserve in well-closed containers.
• Labeling:
When more than one Dissolution test is given, the labeling states the Dissolution test used only if Test 1 is not used.
• USP Reference Standards 11
11
USP Mercaptopurine RS 
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Auxiliary Information—
Please check for your question in the FAQs before contacting USP.
| Topic/Question | Contact | Expert Committee |
|---|---|---|
| Monograph | Feiwen Mao, M.S.
Senior Scientific Liaison 1-301-816-8320 |
(SM32010) Monographs - Small Molecules 3 |
| 711 |
Margareth R.C. Marques, Ph.D.
Senior Scientific Liaison 1-301-816-8106 |
(GCDF2010) General Chapters - Dosage Forms |
| Reference Standards | RS Technical Services 1-301-816-8129 rstech@usp.org |
USP35–NF30 Page 3811
Pharmacopeial Forum: Volume No. 36(6) Page 1554