Isoniazid Tablets

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 

Isoniazid Tablets contain NLT 90.0% and NMT 110.0% of the labeled amount of isoniazid (C₆H₇N₃O). 

2 IDENTIFICATION 

The retention time of the isoniazid peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay. B. Ultraviolet Absorption 

Sample stock solution: Nominally 0.1 mg/mL of isoniazid in water prepared from a portion of finely powdered Tablets Sample solution: Nominally 0.01 mg/mL of isoniazid in water prepared as follows. Transfer 10.0 mL of Sample stock solution to a 100-mL volumetric flask, add 2.0 mL of 0.1 N hydrochloric acid, and dilute with water to volume. 

Acceptance criteria: The UV absorption spectrum of the Sample solution exhibits maxima and minima only at the same wavelengths as that of a similar solution of USP Isoniazid RS, concomitantly measured. 

3 ASSAY 

Procedure 

Buffer: To 0.1 M monobasic potassium phosphate solution, adjusted with 10 N sodium hydroxide to a pH of 6.9, add sufficient triethanolamine to obtain a solution of 0.2 mM of triethanolamine. 

Mobile phase: Buffer and methanol (95:5) 

Standard solution: 0.32 mg/mL of USP Isoniazid RS in Mobile phase 

Sample solution: Nominally 0.32 mg/mL of isoniazid in Mobile phase prepared as follows. Weigh and finely powder NLT 20 Tablets. Transfer a portion of the powder, equivalent to 32 mg of isoniazid, to a 100-mL volumetric flask. Add 40 mL of Mobile phase, and sonicate for 10 min. Cool to room temperature, dilute with Mobile phase to volume, and centrifuge for 5 min. 

Chromatographic system 

(See Chromatography 〈621〉, System Suitability.) 

Mode: LC 

Detector: UV 254 nm 

Column: 3.9-mm × 30-cm; packing L1 

Flow rate: 1.5 mL/min 

Injection volume: 20 µL 

System suitability 

Sample: Standard solution 

Suitability requirements 

Capacity factor, k′: NLT 2.35 

Column efficiency: NLT 1800 theoretical plates 

Tailing factor: NMT 1.5 

Relative standard deviation: NMT 1.0% 

Analysis 

Samples: Standard solution and Sample solution 

Calculate the percentage of the labeled amount of isoniazid (C₆H₇N₃O) in the portion of Tablets taken: 

Result = (r_U/r_S) × (C_S /C_U) × 100 

r_U = peak response from the Sample solution 

r_S = peak response from the Standard solution 

C_S = concentration of USP Isoniazid RS in the Standard solution (mg/mL) 

C_U = nominal concentration of isoniazid in the Sample solution (mg/mL) 

Acceptance criteria: 90.0%–110.0% 

4 PERFORMANCE TESTS 

Dissolution 〈711〉 

Medium: 0.01 N hydrochloric acid; 900 mL 

Apparatus 1: 100 rpm 

Time: 45 min 

Detector: UV 263 nm 

Standard solution: USP Isoniazid RS in Medium 

Sample solution: Dilute with Medium to a nominal concentration that is similar to that of the Standard solution. 

Analysis: Determine the percentage of the labeled amount of isoniazid (C₆H₇N₃O) dissolved by using UV absorption on filtered portions of the

solution under test, suitably diluted with Medium, in comparison with the Standard solution. 

Tolerances: NLT 80% (Q) of the labeled amount of isoniazid (C₆H₇N₃O) is dissolved. 

Change to read: 

Uniformity of Dosage Units 〈905〉: Meet the requirements

Procedure for content uniformity 

Diluent: 0.1 N hydrochloric acid and water (3 in 100) 

Standard solution: 10 µg/mL of USP Isoniazid RS prepared as follows. Dissolve a quantity of USP Isoniazid RS in a volume of water corresponding to that used to dissolve a similar amount of isoniazid from the Tablet, and dilute with Diluent. 

Sample solution: Nominally 10 µg/mL of isoniazid prepared as follows. Transfer 1 finely powdered Tablet to a 500-mL volumetric flask with the aid of 200 mL of water. Shake by mechanical means for 30 min, and add water to volume. Filter, and discard the first 20 mL of the filtrate. Dilute a portion of the filtrate with Diluent. 

Instrumental conditions 

Mode: UV 

Analytical wavelength: 263 nm 

Cell: 1 cm 

Blank: Water 

Calculate the percentage of the labeled amount of isoniazid (C₆H₇N₃O) in the Tablet taken: 

Result = (A_U/A_S) × (C_S /C_U) × 100 

_AU = absorbance of the Sample solution 

_AS = absorbance of the Standard solution 

C_S = concentration of USP Isoniazid RS in the Standard solution (mg/mL) 

C_U = nominal concentration of isoniazid in the Sample solution (mg/mL) 

5 ADDITIONAL REQUIREMENTS 

Packaging and Storage: Preserve in well-closed, light-resistant containers. 

USP Reference Standards 〈11〉 

USP Isoniazid RS