Isoniazid Oral 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 

Isoniazid Oral Solution contains, in each 100 mL, NLT 0.93 g and NMT 1.10 g of isoniazid (C₆H₇N₃O). 

2 IDENTIFICATION 

A.

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 Oral Solution 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 

Nitrite Titration 〈451〉 

Diluent: Dilute hydrochloric acid (1 in 6) 

Sample solution: Nominally 2 mg/mL of isonizid prepared as follows. To a volume of Oral Solution, equivalent to 100 mg of isoniazid, add 50 mL of a mixture of 1 part of potassium bromide in 10 parts of Diluent. 

Analysis: Proceed as directed in the chapter, beginning with “cool to about 15°”. Each mL of 0.1 M sodium nitrite is equivalent to 13.71 mg of isoniazid (C₆H₇N₃O). 

Acceptance criteria: 0.93–1.10 g in each 100 mL 

4 ADDITIONAL REQUIREMENTS 

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

USP Reference Standards 〈11〉 

USP Isoniazid RS