Norethindrone Acetate and Ethinyl Estradiol Tablets

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

Norethindrone Acetate and Ethinyl Estradiol Tablets contain NLT 90.0% and NMT 110.0% of the labeled amount of norethindrone acetate (C₂₂H₂₈O₃), and NLT 88.0% and NMT 112.0% of the labeled amount of ethinyl estradiol (C₂₀H₂₄O₂).

2 IDENTIFICATION

A. The retention times of the major peaks of the Sample solution correspond to those of the Standard solution, as obtained in the Assay.

B. The UV spectra of the major peaks of the Sample solution correspond to those of the Standard solution, as obtained in the Assay.

3 ASSAY

3.1 Procedure

Mobile phase: Acetonitrile, methanol, and water (40:5:55)

Diluent: Acetonitrile and water (50:50)

Standard solution: 0.090 mg/mL of USP Norethindrone Acetate RS and 1.76 µg/mL of USP Ethinyl Estradiol RS in Diluent

Sample solution: Nominally 0.1 mg/mL of norethindrone acetate from Tablets prepared as follows. Transfer an appropriate number of Tablets (NLT 20) to a volumetric flask. Fill the flask with Diluent to about 75% of volume, and disintegrate the Tablets by mechanical shaking and sonication. Allow the solution to equilibrate to room temperature, and dilute with Diluent to volume. Centrifuge a portion of the solution using glass centrifuge tubes, and use the clear supernatant.

Chromatographic system

• (See Chromatography 〈621〉, System Suitability.)
• Mode: LC
• Detector: UV 200 nm. For Identification B, use a diode array detector in the range of 200–600 nm.
• Column: 4.6-mm × 15-cm; 5-µm packing L1
• Flow rate: 1.5 mL/min
• Injection volume: 100 µL
• Run time: NLT 1.2 times the retention time of norethindrone acetate

System suitability

• Sample: Standard solution
• [Note-The relative retention times for ethinyl estradiol and norethindrone acetate are about 0.28 and 1.0, respectively.]
• Suitability requirements
• Resolution: NLT 10.0 between ethinyl estradiol and norethindrone acetate
• Tailing factor: NMT 2.0 for ethinyl estradiol and norethindrone acetate
• Relative standard deviation: NMT 2.0% for ethinyl estradiol and norethindrone acetate

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of norethindrone acetate (C₂₂H₂₈O₃) and ethinyl estradiol (C₂₀H₂₄O₂) in the portion of Tablets taken:

Result = (rᵤ/rₛ) × (Cₛ/Cᵤ) × 100

rᵤ = peak response of norethindrone acetate or ethinyl estradiol from the Sample solution

rₛ = peak response of norethindrone acetate or ethinyl estradiol from the Standard solution

Cₛ = concentration of USP Norethindrone Acetate RS (mg/mL) or USP Ethinyl Estradiol RS (µg/mL) in the Standard solution

Cᵤ = nominal concentration of norethindrone acetate (mg/mL) or ethinyl estradiol (µg/mL) in the Sample solution

Acceptance criteria

• Norethindrone acetate: 90.0%–110.0%
• Ethinyl estradiol: 88.0%–112.0%

4 PERFORMANCE TESTS

Change to read:

4.1 Dissolution 〈711〉

4.1.1 Test 1

0.025 M acetate buffer solution: Transfer 5.22 g of anhydrous sodium acetate and 2.2 g of glacial acetic acid to a 4-L volumetric flask, add 3.5 L of water, and adjust with 1 N sodium hydroxide to a pH of 5.0. Dilute with water to volume.

Medium: 0.025 M acetate buffer solution with 0.15% sodium lauryl sulfate, prepared as follows. Weigh 6 g of sodium lauryl sulfate into a 4-L volumetric flask, add 1.5 L of 0.025 M acetate buffer solution, mix, and dilute with 0.025 M acetate buffer solution to volume; 600 mL.

Apparatus 2: 75 rpm

Time: 60 min

Mobile phase: Acetonitrile, tetrahydrofuran, and 0.2% phosphoric acid (38:8:54)

Standard solution: USP Norethindrone Acetate RS and USP Ethinyl Estradiol RS dissolved in a minimum amount of acetonitrile, and diluted with Medium to obtain a solution having known concentrations equivalent to the expected concentrations of the solution under test

Sample solution: Withdraw a 2-mL aliquot of the solution under test, using a glass pipet or syringe, and centrifuge. Use the supernatant.

[Note-The use of a centrifuge speed of 2000 rpm for 5 min may be suitable.]

Chromatographic system

• (See Chromatography 〈621〉, System Suitability.)
• Mode: LC
• Detectors
• Detector 1: UV 242 nm for norethindrone acetate
• Detector 2: Fluorescence with an excitation wavelength set at 210 nm and an emission wavelength set at 310 nm for ethinyl estradiol
• Columns
• Guard: 4-mm × 1.25-cm; 5-µm packing L1
• Analytical: 6-mm × 4-cm; 3-µm packing L1
• Flow rate: 1 mL/min
• Injection volume: 200 µL

System suitability

• Sample: Standard solution
• Suitability requirements
• Tailing factor: NMT 2.0 for norethindrone acetate and ethinyl estradiol
• Relative standard deviation: NMT 2.5% for norethindrone acetate and ethinyl estradiol

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of norethindrone acetate (C₂₂H₂₈O₃) or ethinyl estradiol (C₂₀H₂₄O₂) dissolved:

Result = (rᵤ/rₛ) × Cₛ × V × (1/L) × 100

rᵤ = peak response of norethindrone acetate or ethinyl estradiol from the Sample solution

rₛ = peak response of norethindrone acetate or ethinyl estradiol from the Standard solution

Cₛ = concentration of USP Norethindrone Acetate RS (mg/mL) or USP Ethinyl Estradiol RS (µg/mL) in the Standard solution

V = volume of Medium, 600 mL

L = label claim of norethindrone acetate (mg/Tablet) or ethinyl estradiol (µg/Tablet)

Tolerances: NLT 80% (Q) of the labeled amounts of norethindrone acetate (C₂₂H₂₈O₃) and ethinyl estradiol (C₂₀H₂₄O₂) are dissolved.

4.1.2 Test 2

If the product complies with this test, the labeling indicates that it meets USP Dissolution Test 2.

Medium: Prepare Medium as directed in Test 1; 600 mL

0.2% phosphoric acid solution: To a suitable volumetric flask add water to about 50% of the flask volume and phosphoric acid equivalent to 0.2% of the flask volume. Dilute with water to volume and mix.

Apparatus 2: 75 rpm

Time: 30 min

Mobile phase: Acetonitrile, tetrahydrofuran, and 0.2% phosphoric acid solution (515:55:470)

Standard stock solution A: 0.0165 mg/mL of USP Norethindrone Acetate RS in acetonitrile. Sonicate to dissolve.

Standard stock solution B: 1.08 µg/mL of USP Ethinyl Estradiol RS in acetonitrile. Sonicate to dissolve.

Standard solution: 0.00165 mg/mL of USP Norethindrone Acetate RS and 0.0324 µg/mL of USP Ethinyl Estradiol RS in Medium from Standard stock solution A and Standard stock solution B prepared as follows. Pipette 10.0 mL of Standard stock solution A and 3.0 mL of Standard stock solution B into a 100-mL volumetric flask. Dilute with Medium to volume.

Sample solution: Centrifuge a portion of the solution under test. Use the supernatant.

[Note-The use of a centrifuge speed of 3000 rpm for 5 min may be suitable.]

Chromatographic system

• (See Chromatography 〈621〉, System Suitability.)
• Mode: LC
• Detectors
• Detector 1: UV 242 nm for norethindrone acetate
• Detector 2: Fluorescence with an excitation wavelength set at 285 nm and an emission wavelength set at 310 nm for ethinyl estradiol
• Column: 4.6-mm × 15-cm; 5-µm packing L1
• Flow rate: 1 mL/min
• Injection volume: 200 µL
• Run time: NLT 1.5 times the retention time of norethindrone acetate

System suitability

• Sample: Standard solution
• [Note-The relative retention times for ethinyl estradiol and norethindrone acetate are 0.6 and 1.0, respectively.]
• Suitability requirements
• Tailing factor: NMT 2.0 for norethindrone acetate and ethinyl estradiol
• Relative standard deviation: NMT 2.5% for norethindrone acetate and ethinyl estradiol

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of norethindrone acetate (C₂₂H₂₈O₃) or ethinyl estradiol (C₂₀H₂₄O₂) dissolved:

Result = (rᵤ/rₛ) × Cₛ × V × (1/L) × 100

rᵤ = peak response of norethindrone acetate or ethinyl estradiol from the Sample solution

rₛ = peak response of norethindrone acetate or ethinyl estradiol from the Standard solution

Cₛ = concentration of USP Norethindrone Acetate RS (mg/mL) or USP Ethinyl Estradiol RS (µg/mL) in the Standard solution

V = volume of Medium, 600 mL

L = label claim of norethindrone acetate (mg/Tablet) or ethinyl estradiol (µg/Tablet)

Tolerances: NLT 80% (Q) of the labeled amounts of norethindrone acetate (C₂₂H₂₈O₃) and ethinyl estradiol (C₂₀H₂₄O₂) are dissolved.

4.2 Uniformity of Dosage Units 〈905〉: Meet the requirements

5 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in well-closed containers. Store at controlled room temperature.

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〉

USP Ethinyl Estradiol RS

USP Norethindrone Acetate RS