Clomiphene Citrate

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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C₂₆H₂₈ClNO.C₆H₈O₇ 598.08

Ethanamine, 2-[4-(2-chloro-1,2-diphenylethenyl)phenoxy]-N,N-diethyl-, 2-hydroxy-1,2,3-propanetricarboxylate (1:1);

2-[p-(2-Chloro-1,2-diphenylvinyl)phenoxy]triethylamine citrate (1:1)

CAS RN®: 50-41-9; UNII: 1B8447E7YI.

1 DEFINITION

Clomiphene Citrate contains NLT 98.0% and NMT 102.0% of a mixture of the (E)- and (Z)-geometric isomers of clomiphene citrate (C₂₆H₂₈ClNO.C₆H₈O₇), calculated on the anhydrous basis. It contains NLT 30.0% and NMT 50.0% of the Z-isomer, [(Z)-2-[4-(2-chloro-1,2-diphenylethenyl)phenoxy]-N,N-diethylethanamine 2-hydroxy-1,2,3-propanetricarboxylate (1:1)]

2 IDENTIFICATION

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

Change to read:

2.2 B. Spectroscopic Identification Tests 〈197〉, Ultraviolet-Visible Spectroscopy: 197U

Medium: 0.1 N hydrochloric acid

Sample solution: 20 µg/mL

Acceptance criteria: Meets the requirements

2.3 C. Identification Tests-General, Citrate 〈191〉

3 ASSAY

3.1 Procedure

Use low-actinic glassware for all solutions.

Mobile phase: Methanol, water, and triethylamine (55:45:0.3). Adjust with phosphoric acid to a pH of 2.5.

System suitability solution: 2 µg/mL of USP Clomiphene Related Compound A RS and 50 µg/mL of USP Clomiphene Citrate RS in Mobile phase

Standard solution: 50 µg/mL of USP Clomiphene Citrate RS in Mobile phase

Sample stock solution: 0.5 mg/mL of Clomiphene Citrate in Mobile phase, filtered

Sample solution: 50 µg/mL of Clomiphene Citrate in Mobile phase from Sample stock solution

Chromatographic system

• (See Chromatography 〈621〉, System Suitability.)
• Mode: LC
• Detector: UV 233 nm
• Column: 4.6-mm × 25-cm; packing L26
• Flow rate: 1 mL/min
• Injection volume: 50 µL

System suitability

• Samples: System suitability solution and Standard solution
• [Note-The relative retention times for clomiphene related compound A, (Z)-isomer, and (E)-isomer are about 0.9, 1.0, and 1.2, respectively.]
• Suitability requirements
• Resolution: NLT 1.0 between clomiphene related compound A and (Z)-isomer; NLT 1.5 between (Z)-isomer and (E)-isomer, System suitability solution
• Column efficiency: NLT 2000 theoretical plates for the (E)-isomer, Standard solution
• Tailing factor: NMT 3.0 for the (E)-isomer, Standard solution
• Relative standard deviation: NMT 2.0% for both (E)- and (Z)-isomers, Standard solution

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of clomiphene citrate (C₂₆H₂₈ClNO.C₆H₈O₇) in the portion of Clomiphene Citrate taken:

Result = [(r_UE + r_UZ)/(r_SE + r_SZ)] × (C_S/C_U) × 100

r_UE = peak response of the (E)-isomer from the Sample solution

r_UZ = peak response of the (Z)-isomer from the Sample solution

r_SE = peak response of the (E)-isomer from the Standard solution

r_SZ = peak response of the (Z)-isomer from the Standard solution

C_S = concentration of USP Clomiphene Citrate RS in the Standard solution (µg/mL)

C_U = concentration of Clomiphene Citrate in the Sample solution (µg/mL)

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

4 OTHER COMPONENTS

4.1 Content of (Z)-isomer

Mobile phase, System suitability solution, Standard solution, Sample solution, Chromatographic system, and System suitability: Proceed as directed in the Assay.

Analysis

Sample: Sample solution

Calculate the percentage of (Z)-isomer in the portion of Clomiphene Citrate taken:

Result = (r_Z/r_T) × 100

r_Z = peak response of the (Z)-isomer from the Sample solution

r_T = sum of all the peak responses of the Sample solution

Acceptance criteria: 30.0%-50.0%

5 IMPURITIES

5.1 Organic Impurities

Use low-actinic glassware for all solutions.

Buffer: Acetonitrile, diethylamine, and water (40:0.8:60). Adjust with phosphoric acid to a pH of 6.2.

Solution A: Buffer and water (90:10)

Solution B: Buffer

Mobile phase: See Table 1.

System suitability stock solution: 0.28 mg/mL of USP Clomiphene Related Compound A RS in Buffer

System suitability solution: 1.25 mg/mL of USP Clomiphene Citrate RS and 0.028 mg/mL of USP Clomiphene Related Compound A RS, prepared as follows. Transfer 12.5 mg of USP Clomiphene Citrate RS into a 10-mL volumetric flask, add 1.0 mL of System suitability stock solution, and dilute with Buffer to volume.

Standard solution: 0.025 mg/mL of USP Clomiphene Citrate RS in Buffer

Sample solution: 1.25 mg/mL of Clomiphene Citrate in Buffer

Chromatographic system

• (See Chromatography 〈621〉, System Suitability.)
• Mode: LC
• Detector: UV 233 nm
• Column: 4.6-mm × 10-cm; 2.6-µm packing L7
• Column temperature: 30°
• Flow rate: 1.5 mL/min
• Injection volume: 10 µL

System suitability

• Samples: System suitability solution and Standard solution
• [Note-See Table 2 for relative retention times.]
• Suitability requirements
• Relative standard deviation: NMT 5.0% from the sum of the peak areas of the (E)- and (Z)-isomers, Standard solution
• Peak-to-valley ratio: The ratio of the height of the clomiphene related compound A peak to the height of the valley between clomiphene related compound A and clomiphene peaks is NLT 15, System suitability solution

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of each impurity in the portion of Clomiphene Citrate taken:

Result = (r_u/r_s) × (C_s/C_u) × (1/F) × 100

r_u = peak response of each impurity from the Sample solution

r_s = sum of the peak responses of (E)- and (Z)-isomers of clomiphene from the Standard solution

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

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

F = relative response factor (see Table 2)

Acceptance criteria: See Table 2. Disregard peaks less than 0.05%.

a {4-[2-(Diethylamino)ethoxy]phenyl}(phenyl)methanone.

b 2,2-Bis{4-[2-(diethylamino)ethoxy]phenyl}-1,2-diphenylethanone.

c 2-{4-[2-(Diethylamino)ethoxy]phenyl}-1,2-diphenylethan-1-one.

d (E,Z)-2-[2-Chloro-4-(2-chloro-1,2-diphenylvinyl)phenoxy]-N,N-diethylethan-1-amine.

e The sum of these geometric isomers is NMT 1.0%.

f (E,Z)-2-{4-[2-Chloro-2-(4-chlorophenyl)-1-phenylvinyl]phenoxy}-N,N-diethylethan-1-amine.

g (E,Z)-2-{4-[1,2-Bis(4-chlorophenyl)vinyl]phenoxy}-N,N-diethylethan-1-amine.

h (E,Z)-2-{4-[1-(4-Benzylphenyl)-2-chloro-2-phenylvinyl]phenoxy}-N,N-diethylethan-1-amine.

6 SPECIFIC TESTS

Water Determination, Method I 〈921〉: NMT 1.0%

7 ADDITIONAL REQUIREMENTS

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

USP Reference Standards 〈11〉

• USP Clomiphene Citrate RS
• USP Clomiphene Related Compound A RS

(E,Z)-2-[4-(1,2-Diphenylvinyl)phenoxy]-N,N-diethylethanamine hydrochloride.

Also known as (E,Z)-2-[4-(1,2-Diphenylethenyl)phenoxy]-N,N-diethylethanamine hydrochloride.

C₂₆H₂₉NO·HCl 407.98