Cetylpyridinium Chloride Lozenges

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 

Cetylpyridinium Chloride Lozenges contain NLT 90.0% and NMT 125.0% of the labeled amount of cetylpyridinium chloride (C₂₁H₃₈ClN.H₂O) in a suitable molded base. 

2 IDENTIFICATION 

A. 

Eluting solvent: Alcohol and 1.2 N hydrochloric acid (7:3) 

Chromatographic column: Pack a pledget of fine glass wool in the base of a 10-mm × 200-mm chromatographic tube. Add styrene– divinylbenzene cation-exchange resin (strong acid form) to form a uniform column 12 cm in height, and top the column with a pledget of fine glass wool. 

Standard solution: 5 µg/mL of USP Cetylpyridinium Chloride RS in Eluting solvent 

Sample solution: Dissolve nominally 500 µg of cetylpyridinium chloride from NLT 20 finely powdered Lozenges in 50 mL of water. Immediately transfer this solution to the Chromatographic column, and discard the eluate. Wash the column, successively, with 200 mL of water, 100 mL of alcohol, 100 mL of water, and 100 mL of 3 N hydrochloric acid. Discard the washings. Elute the column with 80 mL of Eluting solvent. Collect the eluate in a 100-mL volumetric flask, and dilute with the Eluting solvent to volume. 

Instrumental conditions 

(See Ultraviolet-Visible Spectroscopy 〈857〉.) 

Mode: UV 

Wavelength range: 225–300 nm 

Analysis 

Samples: Standard solution and Sample solution 

Acceptance criteria: The UV absorption spectrum of the Sample solution exhibits maxima and minima at the same wavelengths as that of the Standard solution. 

3 ASSAY 

Procedure 

0.004 M sodium lauryl sulfate: Dissolve 1.15 g of sodium lauryl sulfate in 500 mL of water. Add 2 mL of sulfuric acid, and dilute with water to 1000 mL. 

Standardization of 0.004 M sodium lauryl sulfate: Determine the molarity of the solution as follows. To a glass-stoppered 100-mL cylinder transfer 10.0 mL of 0.004 M cetylpyridinium chloride (1.432 mg/mL of USP Cetylpyridinium Chloride RS). Add 5 mL of 2 N sulfuric acid, 20 mL of chloroform, and 1 mL of methyl yellow TS. Titrate with the sodium lauryl sulfate solution with frequent vigorous shaking until the chloroform layer acquires the first permanent orange-pink color. 

Calculate the molarity, and restandardize before each use. [Note—Sulfuric acid is included in this solution to inhibit precipitate formation. If a precipitate forms under storage, discard the solution, and prepare and standardize a fresh solution of 0.004 M sodium lauryl sulfate.] Sample solution: Nominally 0.1 mg/mL of cetylpyridinium chloride prepared as follows. Dissolve an accurately determined number of Lozenges (about 100) in about 400 mL of water in a 500-mL volumetric flask, and dilute with water to volume. Transfer a measured aliquot of this solution, equivalent to about 10 mg of cetylpyridinium chloride, to a glass-stoppered, 100-mL cylinder. Add 5 mL of 2 N sulfuric acid, 20 mL of chloroform, and 1 mL of methyl yellow TS. Insert the stopper, and shake until the chloroform layer develops a bright yellow color. Analysis: Titrate with 0.004 M sodium lauryl sulfate, shaking thoroughly after each addition, until the chloroform layer develops the first permanent orange-pink color. Each mL of 0.004 M sodium lauryl sulfate is equivalent to 1.432 mg of cetylpyridinium chloride (C₂₁H₃₈ClN.H₂O)

Acceptance criteria: 90.0%–125.0% 

4 ADDITIONAL REQUIREMENTS 

Packaging and Storage: Preserve in well-closed containers. 

USP Reference Standards 〈11〉 

USP Cetylpyridinium Chloride RS