Metronidazole 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

Metronidazole Injection is a sterile, isotonic, buffered solution of Metronidazole in Water for Injection. It contains NLT 90.0% and NMT 110.0% of the labeled amount of metronidazole (C₆H₉N₃O₃).

2 IDENTIFICATION

A. The UV (UV-Vis) spectrum of the metronidazole peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay.

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

3 ASSAY

PROCEDURE

Mobile phase: Methanol and water (20:80)

System suitability solution: 1 µg/mL of USP Metronidazole RS and 2 µg/mL of USP Tinidazole Related Compound A RS in Mobile phase

Standard solution: 0.03 mg/mL of USP Metronidazole RS in Mobile phase

Sample solution: Nominally 0.03 mg/mL of metronidazole in Mobile phase prepared as follows. Transfer a portion of Injection to a suitable volumetric flask, and dilute with Mobile phase to volume.

Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 319 nm. For Identification test A, use a diode array detector in the range of 210-800 nm.

Column: 4.6-mm x 15-cm; 5-µm packing L7

Column temperature: 30°

Flow rate: 1 mL/min

Injection volume: 30 µL

System suitability

Samples: System suitability solution and Standard solution

[NOTE-See Table 1 for the relative retention times.]

Suitability requirements

Samples: System suitability solution and Standard solution

[NOTE-See Table 1 for the relative retention times.]

Suitability requirements

Resolution: NLT 4.0 between metronidazole and tinidazole related compound A, System suitability solution

Tailing factor: NMT 2.0, Standard solution

Relative standard deviation: NMT 1.0%, Standard solution

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of metronidazole (C₆H₉N₃O₃) in the portion of Injection 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 Metronidazole RS in the Standard solution (mg/mL)

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

Acceptance criteria: 90.0%-110.0%

4 IMPURITIES

ORGANIC IMPURITIES

Mobile phase, Chromatographic system, and System suitability solution: Proceed as directed in the Assay.

Standard solution: 0.75 µg/mL each of USP Metronidazole RS and USP Tinidazole Related Compound A RS in Mobile phase

Sample solution: Nominally 500 µg/mL of metronidazole prepared as follows. Transfer a portion of Injection to a suitable volumetric flask.

Add Mobile phase equivalent to 50% of the flask size. Sonicate for 2 min. Dilute with Mobile phase to volume, and pass a portion of the solution through a filter of 0.45-µm pore size. Use the filtrate.

System suitability

Samples: System suitability solution and Standard solution

[NOTE-See Table 1 for the relative retention times.]

Suitability requirements

Resolution: NLT 4.0 between metronidazole and tinidazole related compound A, System suitability solution

Relative standard deviation: NMT 1.0%, Standard solution

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of tinidazole related compound A in the portion of Injection taken:

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

r_U = peak response of tinidazole related compound A from the Sample solution

r_S = peak response of tinidazole related compound A from the Standard solution 

C_S = concentration of USP Tinidazole Related Compound A RS in the Standard solution (µg/mL)

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

Calculate the percentage of any individual unspecified impurity in the portion of Injection taken:

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

r_U = peak response for each unspecified impurity from the Sample solution

r_S = peak response of metronidazole from the Standard solution

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

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

Acceptance criteria: See Table 1.

Table 1

5 SPECIFIC TESTS

pH〈791〉: 4.5–7.0

BACTERIAL ENDOTOXINS TEST (85): NMT 0.35 USP Endotoxin Units/mg of metronidazole

PARTICULATE MATTER IN INJECTIONS (788): It meets the requirements for small-volume injections.

OTHER REQUIREMENTS: It meets the requirements in Injections and Implanted Drug Products (1).

6 ADDITIONAL REQUIREMENTS

PACKAGING AND STORAGE: Preserve in single-dose containers of Type I or Type II glass, or in suitable plastic containers, protected from light. Store at controlled room temperature.

USP REFERENCE STANDARDS (11)

USP Metronidazole RS

USP Tinidazole Related Compound A RS

2-Methyl-5-nitroimidazole.

C₄H₅N₃O₂          127.10