Isoniazid Injection

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 Injection is a sterile solution of Isoniazid in Water for Injection. It contains NLT 90.0% and NMT 110.0% of the labeled amount of isoniazid (C₆H₇N₃O). 

2 IDENTIFICATION 

A. The retention time exhibited by isoniazid in the Sample solution corresponds to that of isoniazid in the Standard solution, as obtained in the Assay. 

B.

Sample stock solution: Nominally 0.1 mg/mL of isoniazid in water prepared as follows. Transfer an equivalent to 50 mg of isoniazid from a volume of Injection to a 500-mL volumetric flask, and dilute with water to volume. 

Sample solution: 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 

Mobile phase: 4.4 g/L of Docusate sodium in a mixture of methanol and water (600:400), and adjusted with 2 N sulfuric acid to a pH of 2.5. 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 

Chromatographic system 

(See Chromatography 〈621〉, System Suitability.) 

Mode: LC 

Detector: UV 254 nm 

Column: 4.6-mm × 25-cm; packing L1 

Flow rate: 1.5 mL/min 

Injection volume: 10 µL 

System suitability 

Sample: Standard solution 

Suitability requirements 

Column efficiency: NLT 1800 theoretical plates 

Tailing factor: NMT 2.0 

Relative standard deviation: NMT 2.0% 

Analysis 

Samples: Standard solution and Sample solution 

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

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

r_U = peak response of isoniazid from the Sample solution 

r_S = peak response of isoniazid 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 SPECIFIC TESTS 

pH 〈791〉: 6.0–7.0 

Bacterial Endotoxins Test 〈85〉: Contains NMT 0.3 USP Endotoxin Unit/mg of isoniazid 

Other Requirements: It meets the requirements in Injections and Implanted Drug Products 〈1〉. 

5 ADDITIONAL REQUIREMENTS 

Packaging and Storage: Preserve in single-dose or multiple-dose containers, preferably of Type I glass, protected from light. Labeling: Its package label states that if crystallization has occurred, the Injection should be warmed to redissolve the crystals before use. USP Reference Standards 〈11〉 

USP Isoniazid RS