Tolnaftate 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

Tolnaftate Topical Solution contains NLT 90.0% and NMT 115.0% of the labeled amount of tolnaftate (C₁₉H₁₇NOS).

2 IDENTIFICATION

Change to read:

A. The retention time of the major peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay _{(USP 1-May-2024)}

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 _{(USP 1-May-2024)}

3 ASSAY

Change to read:

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 from a suitable amount of Topical Solution in methanol

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 254 nm. For Identication 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 tolnaftate (C₁₉H₁₇NOS) in the portion of the Topical Solution taken:

Result = (r_u /r_s ) × (C_s /C_u ) × 100

r_u = peak response of tolnaftate from the Sample solution

r_s = peak response of tolnaftate from the Standard solution

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

C_u = nominal concentration of tolnaftate in the Sample solution (mg/mL) _{(USP 1-May-2024)}

Acceptance criteria: 90.0%–115.0%

4 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight containers.

USP Reference Standards 〈11〉

USP Tolnaftate RS