Tolnaftate Topical Powder

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

Tolnaftate Topical Powder contains NLT 90.0% and NMT 110.0% of the labeled amount of tolnaftate (C₁₉H₁₇NOS).

2 IDENTIFICATION

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

Add the following:

B. The UV spectrum of the major peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay.

3 ASSAY

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3.1 Procedure

Solution A: Methanol and water (70:30). To each liter of the solution, add 1 mL of trifluoroacetic acid.

Solution B: Methanol and water (90:10). To each liter of the solution, add 1 mL of trifluoroacetic acid.

Mobile phase: See Table 1.

Table 1

Standard solution: 0.05 mg/mL of USP Tolnaftate RS in methanol

Sample solution: Nominally 0.05 mg/mL of tolnaftate prepared as follows. Transfer a quantity of the Topical Powder equivalent of 2.5 mg of tolnaftate into a 50-mL volumetric flask, add 30 mL of methanol, shake for 1 h, and dilute with methanol to volume. Centrifuge at 8000 rpm for 10 min, pass a portion of the supernatant through a suitable filter of 0.45-µm pore size, and discard the first 2 mL.

Chromatographic system

• (See Chromatography 〈621〉, System Suitability.)
• Mode: LC
• Detector: UV 254 nm. For Identification B, use a diode array detector in the range of 200–400 nm.
• Column: 4.6-mm × 15-cm; 5-µm packing L1
• Temperatures
• Autosampler: 4°
• Column: 30°
• Flow rate: 1 mL/min
• Injection volume: 10 µL

System suitability

• Sample: Standard solution
• Suitability requirements
• Tailing factor: NMT 2.0
• Relative standard deviation: NMT 1.0%

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of tolnaftate (C₁₉H₁₇NOS) in the portion of the Topical Powder taken:

Result = (rᵤ/rₛ) × (Cₛ/Cᵤ) × 100

rᵤ = peak response of tolnaftate from the Sample solution

rₛ = peak response of tolnaftate from the Standard solution

Cₛ = concentration of USP Tolnaftate RS in the Standard solution (mg/mL)

Cᵤ = nominal concentration of tolnaftate in the Sample solution (mg/mL) 

Acceptance criteria: 90.0%–110.0%

4 PERFORMANCE TESTS

Minimum Fill 〈755〉: Meets the requirements

5 ADDITIONAL REQUIREMENTS

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Packaging and Storage: Preserve in tight containers. Store between 2° and 30°.

USP Reference Standards 〈11〉

USP Tolnaftate RS