Guaifenesin 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

Guaifenesin Oral Solution contains NLT 90.0% and NMT 110.0% of the labeled amount of guaifenesin (C₁₀H₁₄O₄).

2 IDENTIFICATION

Change to read:

A. (USP 1-May-2022) The retention time of the guaifenesin peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay.

Add the following:

B. The UV spectrum of the guaifenesin peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay. (USP 1-May-2022)

3 ASSAY

Change to read:

3.1 Procedure

Mobile phase: Methanol, glacial acetic acid, and water (40: 1.5: 60)

Benzoic acid solution: 2 mg/mL of benzoic acid in methanol

Standard stock solution: 2 mg/mL of USP Guaifenesin RS in water. Shake to dissolve.

Standard solution: 40 μg/mL of USP Guaifenesin RS prepared as follows. Transfer 2.0 mL of the Standard stock solution to a 100-mL volumetric flask. Add 45 mL of methanol and dilute with water to volume.

System suitability solution: 100 μg/mL of benzoic acid and 40 μg/mL of USP Guaifenesin RS prepared as follows. Transfer 5.0 mL of Benzoic acid solution and 2.0 mL of Standard stock solution to a 100-mL volumetric flask. Add 40 mL of methanol and dilute with water to volume.

Sample stock solution: Nominally 2 mg/mL of guaifenesin from Oral Solution in water prepared as follows. Transfer a suitable volume of Oral Solution, equivalent to 200 mg of guaifenesin, to a 100-mL volumetric flask. Dilute with water to volume

Sample solution: Nominally 40 μg/mL of guaifenesin prepared as follows. Transfer 2.0 mL of the Sample stock solution to a 100-mL volumetric flask. Add 45 mL of methanol and dilute with water to volume.

3.2 Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 276 nm. For Identification B, use a diode array detector in the range of 200 - 400 nm. (USP 1-May-2022)

Column: 4.6-mm × 25-cm; 10-μm packing L1

Flow rate: 2 mL/min

Injection volume: 20 μL

3.3 System suitability

Samples: Standard solution and System suitability solution

[Note - The relative retention times for guaifenesin and benzoic acid are 0.7 and 1.0, respectively.]

3.4 Suitability requirements

Resolution: NLT 3.0 between guaifenesin and benzoic acid, System suitability solution

Relative standard deviation: NMT 1.0%, (USP 1-May-2022) Standard solution

3.5 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of labeled amount of guaifenesin (C₁₀H₁₄O₄) in the portion of Oral Solution taken:

Result = (r_U/r_S) × (C_S/C_U) × 100

r_U = peak response of guaifenesin from the Sample solution

r_S = peak response of guaifenesin from the Standard solution

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

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

Acceptance criteria: 90.0%–110.0%

4 OTHER COMPONENTS

Alcohol Determination 〈611〉, Method I: (if present) 90.0–115.0% of the labeled amount of alcohol (C₂H₅OH)

5 PERFORMANCE TESTS

Uniformity of Dosage Units 〈905〉

For Oral Solution packaged in single-unit containers: Meets the requirements

Deliverable Volume 〈698〉

For Oral Solution packaged in multiple-unit containers: Meets the requirements

6 SPECIFIC TESTS

Change to read:

pH 〈791〉: 2.3 - 6.5 (USP 1-May-2022)

7 ADDITIONAL REQUIREMENTS

Change to read:

Packaging and Storage: Preserve in tight containers. Do not refrigerate. (USP 1-May-2022)

USP Reference Standards 〈11〉

USP Guaifenesin RS