Cetylpyridinium Chloride Topical Solution

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 Topical Solution contains NLT 95.0% and NMT 105.0% of the labeled amount of cetylpyridinium chloride (C₂₁H₃₈ClN.H₂O)

2 IDENTIFICATION 

A. 

Standard solution: 40 µg/mL of USP Cetylpyridinium Chloride RS in water 

Sample solution: 40 µg/mL of cetylpyridinium chloride from Topical Solution diluted with water 

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. 

B. Identification Tests—General〈191〉, Chloride 

Sample solution: Evaporate on a steam bath a volume of Topical Solution equivalent to 500 mg of cetylpyridinium chloride from Topical Solution to one-half of its original volume. 

Acceptance criteria: The Sample solution meets the requirements of test A, except that when silver nitrate TS is added, turbidity is produced rather than a curdy white precipitate. 

3 ASSAY 

Procedure 

Sample solution: Add a volume of Topical Solution nominally equivalent to 150 mg of cetylpyridinium chloride to a glass-stoppered, 500-mL graduated cylinder. Add 10 mL of chloroform, 0.4 mL of bromophenol blue solution (1 in 2000), and 5 mL of a freshly prepared solution of sodium bicarbonate (4.2 in 1000). 

Analysis: Titrate the Sample solution with 0.02 M sodium tetraphenylboron VS until the blue color disappears from the chloroform layer. Add the last portions of the sodium tetraphenylboron solution dropwise, agitating vigorously after each addition. Each mL of 0.02 M sodium tetraphenylboron is equivalent to 7.160 mg of cetylpyridinium chloride (C₂₁H₃₈ClN.H₂O). 

Acceptance criteria: 95.0%–105.0% 

4 ADDITIONAL REQUIREMENTS 

Packaging and Storage: Preserve in tight containers. 

USP Reference Standards 〈11〉 

USP Cetylpyridinium Chloride RS