Diclofenac Potassium 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 

Diclofenac Potassium Tablets contain NLT 90.0% and NMT 110.0% of the labeled amount of diclofenac potassium (C₁₄H₁₀Cl₂KNO₂).

2 IDENTIFICATION 

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

B. The UV (190–400 nm) spectrum of the diclofenac peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay. 

3 ASSAY 

3.1 Procedure 

Solution A: 0.7708 g/L of ammonium acetate in water. Adjust with acetic acid to a pH of 5.3. Pass through a suitable lter of 0.2-µm pore size. 

Solution B: Acetonitrile 

Mobile phase: See Table 1. 

Table 1 

Diluent: Acetonitrile and water (50:50) 

Standard solution: 0.2 mg/mL of USP Diclofenac Potassium RS in Diluent 

Sample solution: Nominally 0.2 mg/mL of diclofenac potassium in Diluent prepared as follows. Transfer a suitable portion of diclofenac potassium to a suitable volumetric ask from NLT 20 nely powdered Tablets. Add Diluent equivalent to 80% of the ask volume. Dissolve and ll with Diluent to volume. Pass the solution through a suitable lter of 0.22-µm pore size. 

[Note—Protect the Standard solution and Sample solution from light.] 

Chromatographic system 

(See Chromatography 〈621〉, System Suitability.) 

Mode: LC 

Detector: UV 280 nm. For Identication test B, use a photo-diode array detector. 

Column: 10-cm × 2.0-mm; 1.9-µm packing L1 

Column temperature: 35° 

Flow rate: 0.3 mL/min 

Injection volume: 1 µL 

System suitability 

Sample: Standard solution 

[Note—See Table 2 for relative retention times.] 

Suitability requirements 

Tailing factor: NMT 1.2 

Relative standard deviation: NMT 1.0% 

Analysis 

Samples: Standard solution and Sample solution 

Calculate the percentage of the labeled amount of diclofenac potassium (C₁₄H₁₀Cl₂KNO₂) in the portion of Tablets taken:

Result = (r_u/r_s) × (C_s/C_u) × 100

r_u = peak response of diclofenac from the Sample solution 

r_s = peak response of diclofenac from the Standard solution 

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

C_u = nominal concentration of diclofenac potassium in the Sample solution (mg/mL) 

Acceptance criteria: 90.0%–110.0% 

4 PERFORMANCE TESTS 

4.1 Dissolution 〈711〉 

Medium: Simulated intestinal uid (without enzyme); 900 mL

Apparatus 2: 50 rpm 

Time: 60 min 

Standard solution: A known concentration of USP Diclofenac Potassium RS in Medium. Pass a portion of the solution under test through a suitable lter of 0.45-µm pore size. Dilute with Medium if necessary. 

Sample solution: Sample as per Dissolution 〈711〉. Dilute with Medium to a concentration that is similar to the Standard solution. Instrumental conditions 

Mode: UV-Vis 

Analytical wavelength: Maximum absorbance at about UV 276 nm 

Analysis 

Samples: Standard solution and Sample solution 

Calculate the percentage of the labeled amount of diclofenac potassium (C₁₄H₁₀Cl₂KNO₂) dissolved: 

(A_U  × C_S  ×  V × 100)/(A_S  × L) 

A_U= absorbance of the Sample solution 

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

V = volume of Medium, 900 mL 

A_S = absorbance of the Standard solution 

L = label claim of diclofenac potassium (mg/Tablet) 

Tolerances: NLT 75% (Q) of the labeled amount of diclofenac potassium (C₁₄H₁₀Cl₂KNO₂) is dissolved. 

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

5 IMPURITIES 

5.1 Organic Impurities 

Mobile phase and Diluent: Proceed as directed in the Assay. 

Standard solution: 0.001 mg/mL each of USP Diclofenac Potassium RS and USP Diclofenac Related Compound A RS in Diluent Sample solution: Nominally 1.0 mg/mL of diclofenac potassium in Diluent prepared as follows. Transfer a suitable portion of diclofenac potassium to a suitable volumetric ask from NLT 20 nely powdered Tablets. Add Diluent equivalent to 80% of the ask volume. Dissolve and ll with Diluent to volume. Pass the solution through a suitable lter of 0.22-µm pore size. 

Chromatographic system: Proceed as directed in the Assay except for the Detector. 

Detector: UV 254 nm 

Sample: Standard solution 

Suitability requirements 

Relative standard deviation: NMT 5% 

Signal-to-noise ratio: NLT 10 

Analysis 

Samples: Standard solution and Sample solution 

Calculate the percentage of diclofenac related compound A in the portion of Tablets taken: 

Result = (r_u/r_s) × (C_s/C_u) × 100

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

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

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

C_u = nominal concentration of diclofenac potassium in the Sample solution (mg/mL) 

Calculate the percentage of any other impurity in the portion of Tablets taken: 

Result = (r_u/r_s) × (C_s/C_u) × 100

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

r_s = peak response of diclofenac from the Standard solution 

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

C_u = nominal concentration of diclofenac potassium in the Sample solution (mg/mL) 

Acceptance criteria: See Table 2. Disregard any impurity peak less than 0.05%. 

Table 2 

a 1,3-Dihydro-2H-indol-2-one. 

b Process-related impurities, not to be counted in total impurities. 

c 2-{2-[(2-Bromo-6-chlorophenyl)amino]phenyl}acetic acid. 

d {2-[(2,6-Dichlorophenyl)amino]phenyl}methanol. 

e 2-[(2,6-Dichlorophenyl)amino]benzaldehyde. 

6 ADDITIONAL REQUIREMENTS 

6.1 Packaging and Storage:

Preserve in tight, light-resistant containers, and store at controlled room temperature. 

6.2 USP Reference Standards 〈11〉 

USP Diclofenac Potassium RS 

USP Diclofenac Related Compound A RS 

1-(2,6-Dichlorophenyl)indolin-2-one (diclofenac lactam). 

C₁₄H₉Cl₂NO         278.13