Cidofovir

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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C₈H₁₄N₃O₆P. 2H₂O               315.22

Phosphonic acid, [[2-(4-amino-2-oxo-1(2H)-pyrimidyl)-1-(hydroxymethyl)ethoxy]methyl]-, dihydrate, (S)-;

1-[(S)-3-Hydroxy-2-(phosphonylmethoxy)propyl]cytosine dihydrate CAS RN®: 149394-66-1.

Anhydrous

279.19 CAS RN®: 113852-37-2.

C₈H₁₄N₃O₆P

1 DEFINITION

Cidofovir contains NLT 98.0% and NMT 102.0% of cidofovir (C₈H₁₄N₃O₆P), 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 Sample solution corresponds to that of the Standard solution, as obtained in the Assay.

3 ASSAY

3.1 PROCEDURE

[NOTE-Solutions containing cidofovir are stable at room temperature for 8 8 h.]

Solution A: Acetonitrile and water (40:60)

Buffer: Dissolve 1.2 g of dibasic ammonium phosphate and 2.0 g of tetrabutylammonium phosphate in 1 L of water. Adjust with ammonium hydroxide to a pH of 9.2.

Mobile phase: Solution A and Buffer (22:78)

Standard solution: 0.1 mg/mL of USP Cidofovir RS in water

Sample solution: 0.1 mg/mL of Cidofovir in water

Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 274 nm

Column: 4.6-mm x 25-cm; 5-µm packing 11

Column temperature: 30°

Flow rate: 1 mL/min

Injection volume: 20 µL

3.2 System suitability

Sample: Standard solution

3.3 Suitability requirements

Tailing factor: 0.8-1.5

Relative standard deviation: NMT 0.73%

3.4 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of cidofovir (C₈H₁₄N₃O₆P) in the portion of Cidofovir taken:

Result = (r_U/r_S) x (C_S/C_U) × 100

r_U = peak response from the Sample solution

r_S = peak response from the Standard solution

C_S = concentration of USP Cidofovir RS in the Standard solution (mg/mL)

C_U = concentration of Cidofovir in the Sample solution (mg/mL)

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

4 IMPURITIES

Delete the following:

4.1 RESIDUE ON IGNITION (281)

Analysis: Perform the ignition at 850 ± 50"; silica crucibles are suitable.

Acceptance criteria: NMT 0.5% (RB 1-Jun-2019)

4.2 ORGANIC IMPURITIES

[NOTE-Solutions containing cidofovir are stable at room temperature for 8 h.]

Mobile phase and Chromatographic system: Proceed as directed in the Assay with a run time four times the retention time of cidofovir.

System suitability solution: 1,5 µg/mL each of USP Cidofovir Related Compound A RS and USP Cidofovir Related Compound B. RS in water

Standard solution: 0.001 mg/mL of USP Cidofovir RS in water

Sample solution: 1 mg/mL of Cidofovir in water

System suitability

Samples: System suitability solution and Standard solution

[NOTE-See Table 1 for relative retention times.]

Suitability requirements

Resolution: NLT 1.5 between cidofovir related compound A and cidofovir related compound B, System suitability solution

Relative standard deviation: NMT 5%, Standard solution

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of each individual impurity in the portion of Cidofovir taken:

Result = (r_U/r_S) x (C_S/C_U) × (1/F) × 100

r_U = peak response of each individual impurity from the Sample solution

r_S = peak response of cidofovir from the Standard solution

C_S = concentration of USP Cidofovir RS in the Standard solution (mg/mL)

C_U = concentration of Cidofovir in the Sample solution (mg/mL)

Frelative response factor (see Table 1)

Acceptance criteria

Individual impurities: See Table 1. Disregard any impurity peaks less than 0.02%.

Table 1

^a 1-[(S)-2,3-Dihydroxypropyl cytosine.

^b 1-[(S)-3-Hydroxy-2-(phosphonomethoxy)propyl]uracil.

^c 1-[(S)-3-Bromo-2-(phosphonomethoxy)propyl]cytosine.

5 ENANTIOMERIC PURITY

Mobile phase: Dissolve 1.0 g of cupric sulfate in 1 L of water. Add 1.32 g of phenylalanine and sonicate to dissolve.

System suitability solution: 1 mg/mL of USP Cidofovir RS and 0.01 mg/mL of USP Cidofovir Enantiomer RS in water

Standard solution: 0.01 mg/mL of USP Cidofovir Enantiomer RS in water

Sample solution: 1 mg/mL of Cidofovir in water

Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 280 nm

Column: 4.6-mm x 25-cm; 5-µm packing L1

Temperatures

Autosampler: 15°

Column: 15°

Flow rate: 0.5 mL/min

Injection volume: 10 µL

Run time: Two times the retention time of cidofovir

System suitability

Samples: System suitability solution and Standard solution

[NOTE-Typical relative retention times for cidofovir and cidofovir enantiomer are 1.0 and 1.3, respectively.]

Suitability requirements

Resolution: NLT 2.0 between cidofovir and cidofovir enantiomer, System suitability solution

Relative standard deviation: NMT 5%, Standard solution

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of cidofovir enantiomer in the portion of Cidofovir taken:

Result = (r_U/r_S) x (C_S/C_U) × 100

r_U = peak response of cidofovir enantiomer from the Sample solution

r_S = peak response of cidofovir enantiomer from the Standard solution s

C_S = concentration of USP Cidofovir Enantiomer RS in the Standard solution (mg/mL)

C_U = concentration of Cidofovir in the Sample solution (mg/mL)

Acceptance criteria: NMT 1.0%

6 SPECIFIC TESTS

Microbial Enumeration Tests 〈61〉 and Tests for Specified Microorganisms 〈62〉: The total aerobic bacterial count is NMT 10² cfu/g. The total combined molds and yeasts count is NMT 10¹ cfu/g.

Water Determination 〈921〉, Method I, Method Ia

Sample: 0.2 g

Acceptance criteria: 10.5%–12.5%

pH 〈791〉

Sample solution: 1 g in 100 mL of water

Acceptance criteria: 2.5–4.5

7 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight containers at controlled room temperature.

USP Reference Standards 〈11〉

USP Cidofovir RS

USP Cidofovir Enantiomer RS

1-[(R)-3-Hydroxy-2-(phosphonomethoxy)propyl]cytosine dihydrate.

C₈H₁₄N₃O₆P . 2H₂O 315.22

USP Cidofovir Related Compound A RS

1-[(S)-3-Hydroxy-2-(O-ethylphosphonomethoxy)propyl]cytosine.

C₁₀H₁₈N₃O₆P 307.24

USP Cidofovir Related Compound B RS

1-[(S)-3-Hydroxy-2-(O,O-diethylphosphonomethoxy)propyl]cytosine hydrochloride.

C₁₂H₁₂N₃O₆P · HCl 371.76