Didanosine

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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1 DEFINITION 

Didanosine contains NLT 98.0% and NMT 102.0% of C₁₀H₁₂N₄O₃, calculated on the anhydrous basis. 

2 IDENTIFICATION 

Change to read: 

A. Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197K (CN 1-May-2020) 

B. The retention time of the major peak from the Sample solution corresponds to that of the Standard solution, as obtained in the Assay. 

3 ASSAY 

3.1 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 

(See Chromatography 〈621〉, System Suitability.) 

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 eciency: 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 = (r_u/r_s) × (C_s/C_u) × 100

r_u = peak response of the Sample solution 

r_s = peak response of the Standard solution 

C_s = concentration of the Standard solution (mg/mL) 

C_u = concentration of the Sample solution (mg/mL) 

Acceptance criteria: 98.0%–102.0% on the anhydrous basis 

4 IMPURITIES 

4.1 Residue on Ignition 〈281〉: NMT 0.2% 

Change to read: 

4.2 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 (ERR 1-Jun-2019) 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 

Chromatographic system 

(See Chromatography 〈621〉, System Suitability.) 

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 eciency: 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 = (r_u/r_s) × (C_s/C_u) × 100

r_u = peak response of didanosine related compound A from the Sample solution 

r_s = peak response of didanosine related compound A from the Standard solution 

C_s = concentration of USP Didanosine Related Compound A RS in the Standard solution (mg/mL) 

C_u = concentration of didanosine in the Sample solution (mg/mL) 

Calculate the percentage of all other impurities in the portion of Didanosine taken: 

Result = (r_u/r_s) × (C_s/C_u) × 100

r_u = peak response of the Sample solution 

r_s = peak response of the Standard solution 

C_s = concentration of USP Didanosine RS in the Standard solution (mg/mL) 

C_u = concentration of the Sample solution (mg/mL) 

Acceptance criteria: See Table 2. 

Table 2 

5 SPECIFIC TESTS 

5.1 Optical Rotation, Specific Rotation 〈781S〉 

Sample solution: 10 mg/mL in water 

Acceptance criteria: −28° to −24°, anhydrous 

5.2 Water Determination, Method I 〈921〉: NMT 2.0% 

6 ADDITIONAL REQUIREMENTS 

6.1 Packaging and Storage:

Preserve in well-closed containers, and store at controlled room temperature.

6.2 USP Reference Standards 〈11〉 

USP Didanosine RS 

USP Didanosine Related Compound A RS 

Hypoxanthine. 

USP Didanosine Related Compound B RS 

2′,3′-Dideoxyadenosine. 

USP Didanosine System Suitability Mixture RS