Ethionamide

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

Ethionamide contains NLT 98.0% and NMT 102.0% of ethionamide (C₈H₁₀N₂S), calculated on the anhydrous basis.

2 IDENTIFICATION

A. Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197K

B. Spectroscopic Identification Tests 〈197〉, Ultraviolet-Visible Spectroscopy: 197U

Standard solution and Sample solution: Prepare as directed in the Assay.

Acceptance criteria: Meets the requirements

3 ASSAY

Procedure

Standard solution: 10 μg/mL of USP Ethionamide RS in methanol

Sample solution: 10 μg/mL of Ethionamide in methanol

Instrumental conditions

Mode: UV

Analytical wavelength: 290 nm

Cell: 1 cm

Blank: Methanol

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of ethionamide (C₈H₁₀N₂S) in the portion of Ethionamide taken:

Result = (A_U/A_S) × (C_S/C_U) × 100

A_U = absorbance of the Sample solution

A_S = absorbance of the Standard solution

C_S = concentration of USP Ethionamide RS in the Standard solution (μg/mL)

C_U = concentration of Ethionamide in the Sample solution (μg/mL)

Acceptance criteria: 98.0%–102.0% on the anhydrous basis

4 IMPURITIES

Residue on Ignition 〈281〉: NMT 0.2%

Delete the following:

Selenium 〈291〉 (USP 1-Dec-2022)

5 SPECIFIC TESTS

Melting Range or Temperature 〈741〉: 158°–164°

pH 〈791〉

Sample solution: 10 mg/mL in water. The solution is slurry.

Acceptance criteria: 6.0–7.0

Water Determination 〈921〉, Method I: NMT 2.0%

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight containers.

USP Reference Standards 〈11〉

USP Ethionamide RS