Didanosine
C10H12N4O3 236.23
Inosine, 2¢,3¢-dideoxy-;
2¢,3¢-Dideoxyinosine
[69655-05-6].
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C10H12N4O3 236.23
Inosine, 2¢,3¢-dideoxy-;
2¢,3¢-Dideoxyinosine
[69655-05-6].DEFINITION
Didanosine contains NLT 98.0% and NMT 102.0% of C10H12N4O3, calculated on the anhydrous basis.
IDENTIFICATION
• B.
The retention time of the major peak from the Sample solution corresponds to that of the Standard solution, as obtained in the Assay.
ASSAY
• Procedure
Buffer:
0.77 g/L of ammonium acetate in water
Mobile phase:
Acetonitrile and Buffer (1:21)
Standard solution:
0.1 mg/mL of USP Didanosine RS in water
Sample solution:
0.1 mg/mL of Didanosine in water
[Note—Mix for 1 h to dissolve completely before use. ]
Chromatographic system
Mode:
LC
Detector:
UV 254 nm
Column:
4.6-mm × 25-cm; packing L1
Flow rate:
2 mL/min
Injection size:
20 µL
System suitability
Sample:
Standard solution
[Note—The retention time of didanosine is between 7 and 11 min. ]
Suitability requirements
Column efficiency:
NLT 6000 theoretical plates
Tailing factor:
NMT 2.5
Relative standard deviation:
NMT 2.0%
Analysis
Samples:
Standard solution and Sample solution
Calculate the percentage of didanosine (C10H12N4O3) in the portion of Didanosine taken:
Result = (rU/rS) × (CS/CU) × 100
| rU | = | = peak response from the Sample solution |
| rS | = | = peak response from the Standard solution |
| CS | = | = concentration of the Standard solution (mg/mL) |
| CU | = | = concentration of the Sample solution (mg/mL) |
Acceptance criteria:
98.0%–102.0% on the anhydrous basis
IMPURITIES
• Residue on Ignition 
281
:
NMT 0.2%
281:
NMT 0.2%
• Heavy Metals, Method II 231:
NMT 20 ppm
231:
NMT 20 ppm
• Related Compounds
Buffer:
Prepare as directed in the Assay.
Diluent:
Adjust the pH of the Buffer with sodium hydroxide to 9. Prepare a mixture of acetonitrile and Buffer (1:19).
Solution A:
Acetonitrile and Buffer (1:19)
Solution B:
Acetonitrile and Buffer (1:3)
System suitability solution:
0.5 mg/mL of of didanosine from USP Didanosine System Suitability Mixture RS in Diluent
Standard stock solution A:
0.05 mg/mL of USP Didanosine Related Compound A RS in Diluent
Standard stock solution B:
0.025 mg/mL of USP Didanosine RS in Diluent
Standard stock solution C:
0.025 mg/mL of USP Didanosine Related Compound B RS in Diluent
Standard solution:
5 µg/mL of USP Didanosine Related Compound A RS, 1.5 µg/mL of USP Didanosine RS, and 1.5 µg/mL of USP Didanosine Related Compound B RS from a mixture of Standard stock solution A, Standard stock solution B, and Standard stock solution C, respectively, diluted with Diluent
Sample solution:
0.5 mg/mL of Didanosine in Diluent
Mobile phase:
See Table 1.
Table 1
| Time (min) |
Solution A (%) |
Solution B (%) |
|---|---|---|
| 0 | 100 | 0 |
| 15 | 100 | 0 |
| 20 | 0 | 100 |
| 30 | 0 | 100 |
| 35 | 100 | 0 |
| 45 | 100 | 0 |
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:
10 µL
System suitability
Samples:
System suitability solution and Standard solution
[Note—Didanosine elutes between 6 and 7.5 min; the relative retention times for didanosine, didanosine related compound A, and didanosine related compound B are 1.0, 0.28, and 2.11, respectively. ]
Suitability requirements
Resolution:
NLT 3.0 between didanosine and dideoxydidehydroinosine, System suitability solution
Column efficiency:
NLT 6000 theoretical plates for dideoxydidehydroinosine, System suitability solution
Relative standard deviation:
NMT 2.0% for didanosine related compound A, Standard solution
Analysis
Samples:
Standard solution and Sample solution
Calculate the percentage of didanosine related compound A in the portion of Didanosine taken:
Result = (rU/rS) × (CS/CU) × 100
| rU | = | = peak response of didanosine related compound A from the Sample solution |
| rS | = | = peak response of didanosine related compound A from the Standard solution |
| CS | = | = concentration of USP Didanosine Related Compound A RS in the Standard solution (mg/mL) |
| CU | = | = concentration of didanosine in the Sample solution (mg/mL) |
Calculate the percentage of all other impurities in the portion of Didanosine taken:
Result = (rU/rS) × (CS/CU) × 100
| rU | = | = peak response of each impurity in the Sample solution |
| rS | = | = peak response for didanosine from the Standard solution |
| CS | = | = concentration of USP Didanosine RS in the Standard solution (mg/mL) |
| CU | = | = concentration of the Sample solution (mg/mL) |
Acceptance criteria:
See Table 2.
Table 2
| Name | Relative Retention Time |
Acceptance Criteria, NMT (%) |
|---|---|---|
| Didanosine related compound A |
0.28 | 0.5 |
| Inosine | 0.39 | 0.2 |
| 2¢-Deoxyinosine | 0.45 | 0.3 |
| 3¢-Deoxyinosine | 0.51 | 0.2 |
| 2¢,3'-Anhydroinosine | 0.59 | 0.2 |
| Dideoxydidehydroinosine | 0.81 | 0.2 |
| Didanosine | 1.0 | — |
| Didanosine related compound B |
2.1 | 0.2 |
| 5¢-Deoxydideoxyadenosine | 3.1 | 0.2 |
| Any other individual, unidentified impurity |
— | 0.1 |
| Total impurities | — | 1.0 |
SPECIFIC TESTS
• Optical Rotation, Specific Rotation 781S
781S
Sample solution:
10 mg/mL in water
Acceptance criteria:
28
to 24, anhydrous
28 to 24, anhydrous
• Water Determination, Method I 921:
NMT 2.0%
921:
NMT 2.0%
ADDITIONAL REQUIREMENTS
• Packaging and Storage:
Preserve in well-closed containers, and store at controlled room temperature.
• USP Reference Standards 11
11
USP Didanosine RS 
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USP Didanosine Related Compound A RS
Hypoxanthine.
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USP Didanosine Related Compound B RS
2¢,3¢-Dideoxyadenosine.
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USP Didanosine System Suitability Mixture RS
Auxiliary Information—
Please check for your question in the FAQs before contacting USP.
| Topic/Question | Contact | Expert Committee |
|---|---|---|
| Monograph | Behnam Davani, Ph.D., M.B.A.
Senior Scientific Liaison 1-301-816-8394 |
(SM12010) Monographs - Small Molecules 1 |
| Reference Standards | RS Technical Services 1-301-816-8129 rstech@usp.org |
USP35–NF30 Page 2888
Pharmacopeial Forum: Volume No. 34(1) Page 87