Docusate Potassium Capsules

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

Docusate Potassium Capsules contain NLT 90.0% and NMT 110.0% of the labeled amount of docusate potassium (C₂₀H₃₇KO₇S).

2 IDENTIFICATION

A. 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

Diluent: Transfer 180 mL of water to a 1000-mL volumetric flask, and dilute with methanol to volume.

Tetrabutylammonium hydroxide solution: 250 mg/mL of tetrabutylammonium hydroxide in methanol

Mobile phase: Mix 180 mL of water, 6.0 mL of glacial acetic acid, and 8.0 mL of Tetrabutylammonium hydroxide solution in a 1000-mL volumetric flask, and dilute with methanol to volume. The water concentration may be varied to meet System suitability requirements and to provide a suitable elution time (about 5 min) for docusate potassium.

Standard solution: 4 mg/mL of USP Docusate sodium RS, calculated on the anhydrous basis, in Diluent

Sample solution

Solid-filled capsules: Open and empty into a suitable container the contents of a counted number of Capsules, nominally equivalent to 1000 mg of docusate potassium. Place the Capsule shells in the container, and add 250.0 mL of Diluent. Shake by mechanical means for 20 min, and clarify a portion of the mixture by centrifuging. Pass a portion of the clear supernatant through a membrane filter of 0.5 μm or finer pore size.

Solution-filled capsules: Cut open a counted number of Capsules, nominally equivalent to 2.5 g of docusate potassium, and place the shells and contents in a suitable container. Add 25 mL of methanol, agitate for NLT 2 min, and decant the liquid into a 200-mL volumetric flask. Repeat the addition of methanol, agitation, and decanting NLT four times. Dilute with methanol to volume. Pipet 8 mL of this solution into a 25-mL volumetric flask, add 4.5 mL of water, and dilute with methanol to volume.

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: Refractive index

Column: 4.6-mm × 25-cm; packing L1

Flow rate: 1.8 mL/min

Injection volume: 100 μL

System suitability

Sample: Standard solution

Suitability requirements

Relative standard deviation: NMT 3.0% for five replicate injections

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of docusate potassium (C₂₀H₃₇KO₇S) in the portion of Capsules taken:

Result = (r_U/r_S) × (C_S/C_U) × (M_r1/M_r2) × 100

r_U = peak response from the Sample solution

r_S= peak response from the Standard solution

C_S= concentration of anhydrous USP Docusate Sodium RS in the Standard solution (mg/mL)

C_U= nominal concentration of docusate potassium in the Sample solution (mg/mL)

M_r1= molecular weight of docusate potassium, 460.67

M_r2= molecular weight of docusate sodium, 444.56

Acceptance criteria: 90.0%–110.0%

4 PERFORMANCE TESTS

Dissolution 〈711〉

Medium: Water; 500 mL

Apparatus 2: 50 rpm

Time: 15 min

Analysis: Place 1 Capsule in each vessel, and allow the Capsule to sink to the bottom of the vessel before starting rotation of the blade.

Observe the Capsules, and record the time taken for each Capsule shell to rupture.

Tolerances: The requirements are met if all of the Capsules tested rupture in NMT 15 min. If 1 or 2 of the Capsules rupture in more than 15 min but NMT 30 min, repeat the test on 12 additional Capsules. NMT 2 of the total of 18 Capsules tested rupture in more than 15 min but NMT 30 min.

Uniformity of Dosage Units 〈905〉: Meet the requirements for Content Uniformity for solid-filled capsules and meet the requirements for Weight Variation for solution-filled capsules

5 ADDITIONAL REQUIREMENTS

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

USP Reference Standards 〈11〉

USP Docusate Potassium RS

USP Docusate Sodium RS