Emtricitabine

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

Emtricitabine contains NLT 98.0% and NMT 102.0% of emtricitabine (C₈H₁₀FN₃O₃S), calculated on the dried basis.

2 IDENTIFICATION

A. Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197K

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

3 ASSAY

Procedure

Solution A: 2.72 g/L of potassium phosphate monobasic in water

Solution B: Methanol and Solution A (80:20)

Mobile phase: See Table 1.

Table 1

Standard solution: 1 mg/mL of USP Emtricitabine RS in water. Sonicate, if necessary, to dissolve prior to final dilution.

Sample solution: 1 mg/mL of Emtricitabine in water. Sonicate, if necessary, to dissolve prior to final dilution.

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 280 nm

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

Column temperature: 40°

Flow rate: 1.2 mL/min

Injection volume: 20 μL

System suitability

Sample: Standard solution

Suitability requirements

Tailing factor: NMT 2.0

Relative standard deviation: NMT 0.73%

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of emtricitabine (C₈H₁₀FN₃O₃S) in the portion of Emtricitabine taken:

Result = (r_U/r_S) × (C_S/C_U) × 100

r_U = peak response of emtricitabine from the Sample solution

r_S = peak response of emtricitabine from the Standard solution

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

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

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

4 IMPURITIES

Residue on Ignition 〈281〉: NMT 0.1%

Organic Impurities

Solution A, Solution B, Mobile phase, Sample solution, and Chromatographic system: Proceed as directed in the Assay.

System suitability solution: 1 mg/mL of USP Emtricitabine System Suitability Mixture B RS in water. Sonicate, if necessary, to dissolve prior to final dilution.

Standard solution: 1 μg/mL of USP Emtricitabine RS in water prepared from the Standard solution in the Assay

Sensitivity solution: 0.5 μg/mL of USP Emtricitabine RS in water prepared from the Standard solution

System suitability

Samples: System suitability solution, Standard solution, and Sensitivity solution

Suitability requirements

Resolution: NLT 1.5 between emtricitabine and emtricitabine 5-fluorouracil analog, System suitability solution

Relative standard deviation: NMT 5.0%, Standard solution

Signal-to-noise ratio: NLT 10, Sensitivity solution

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of any impurity in the portion of Emtricitabine taken:

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

r_U = peak response of any impurity from the Sample solution

r_S = peak response of emtricitabine from the Standard solution

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

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

F = relative response factor (see Table 2)

Acceptance criteria: See Table 2. Disregard the peak due to the emtricitabine diastereomer with a relative retention time of 1.04, if present, as it is monitored in a separate method.

Table 2

^a 4-Amino-5-fluoropyrimidin-2(1H)-one.

^b cis-5-[4-Amino-5-fluoro-2-oxopyrimidin-1(2H)-yl]-1,3-oxathiolane-2-carboxylic acid.

^c 4-Amino-5-fluoro-1-[(2R,3S,5S)-2-(hydroxymethyl)-3-oxo-1,3-oxathiolan-5-yl]pyrimidin-2(1H)-one.

^d 4-Amino-5-fluoro-1-[(2R,3R,5S)-2-(hydroxymethyl)-3-oxo-1,3-oxathiolan-5-yl]pyrimidin-2(1H)-one.

^e 1-[(2R,5S)-2-(Hydroxymethyl)-1,3-oxathiolan-5-yl]cytosine.

^f 5-Fluoro-1-[(2R,5S)-2-(hydroxymethyl)-1,3-oxathiolan-5-yl]uracil.

Enantiomeric and Diastereomeric Purity

Mobile phase: n-Hexane, Ethanol, methanol, trifluoroacetic acid, and diethylamine (800:150:50:1:1)

Diluent: Methanol and Mobile phase (10:90)

System suitability solution: 1 mg/mL of USP Emtricitabine System Suitability Mixture A RS prepared as follows. Transfer a suitable amount of USP Emtricitabine System Suitability Mixture A RS to a suitable volumetric flask. Add about 10% volume of methanol to dissolve. Dilute with Mobile phase to volume.

Standard stock solution: 0.3 mg/mL of USP Emtricitabine RS prepared as follows. Transfer a suitable amount of USP Emtricitabine RS to a suitable volumetric flask. Add about 10% volume of methanol to dissolve. Dilute with Mobile phase to volume.

Standard solution: 3 μg/mL of USP Emtricitabine RS in Diluent prepared from the Standard stock solution

Sample solution: 1 mg/mL of Emtricitabine prepared as follows. Transfer a suitable amount of emtricitabine to a suitable volumetric flask.

Add about 10% volume of methanol to dissolve. Dilute with Mobile phase to volume.

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 280 nm

Column: 4.6-mm × 25-cm; 5-μm packing L51

Flow rate: 1 mL/min

Injection volume: 20 μL

Run time: NLT 2 times the retention time of emtricitabine

System suitability

Samples: System suitability solution and Standard solution

Suitability requirements

Resolution: NLT 2.0 between emtricitabine and emtricitabine 5-epimer, System suitability solution

Relative standard deviation: NMT 5.0%, Standard solution

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the enantiomer and diastereomers in the portion of Emtricitabine taken:

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

r_U = peak response of the enantiomer and diastereomers from the Sample solution

r_S = peak response of emtricitabine from the Standard solution

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

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

F = relative response factor (see Table 3)

Acceptance criteria: See Table 3.

Table 3

^a 5-Fluoro-1-[(2S,5R)-2-(hydroxymethyl)-1,3-oxathiolan-5-yl]cytosine.

^b 5-Fluoro-1-[(2R,5R)-2-(hydroxymethyl)-1,3-oxathiolan-5-yl]cytosine.

^c Use the sum of the areas of both emtricitabine 5-epimer and emtricitabine 2-epimer in the calculation.

^d 5-Fluoro-1-[(2S,5S)-2-(hydroxymethyl)-1,3-oxathiolan-5-yl]cytosine.

5 SPECIFIC TESTS

Loss on Drying 〈731〉

Analysis: Dry at 105° for 3 h.

Acceptance criteria: NMT 0.5%

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight, light-resistant containers. Store at controlled room temperature.

USP Reference Standards 〈11〉

USP Emtricitabine RS

USP Emtricitabine System Suitability Mixture A RS

This is a mixture containing the following components:

Emtricitabine.

Emtricitabine 5-epimer: 5-Fluoro-1-[(2R,5R)-2-(hydroxymethyl)-1,3-oxathiolan-5-yl]cytosine.

C₈H₁₀FN₃O₃S 247.24

USP Emtricitabine System Suitability Mixture B RS

This is a mixture containing the following components:

Emtricitabine.

Emtricitabine 5-fluorouracil analog: 5-Fluoro-1-[(2R,5S)-2-(hydroxymethyl)-1,3-oxathiolan-5-yl]uracil.

C₈H₉FN₂O₄S 248.22▲ (USP 1-May-2023)