Methocarbamol 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

Methocarbamol Injection is a sterile solution of Methocarbamol in an aqueous solution of Polyethylene Glycol 300. It contains NLT 95.0% and NMT 105.0% of the labeled amount of methocarbamol (C₁₁H₁₅NO₅).

2 IDENTIFICATION

Change to read:

A. Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197K (CN 1-May-2020)

Sample: Mix a volume with 40 mL of water equivalent to 500 mg of methocarbamol from Injection in a small separator. Extract with 10 mL of ethyl acetate, and dry the ethyl acetate layer over anhydrous sodium sulfate. Evaporate the ethyl acetate with the use of a water bath maintained at 40° under a stream of nitrogen to dryness.

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

Buffer: 6.8 g/L of monobasic potassium phosphate in water. Adjust with phosphoric acid or potassium hydroxide to a pH of 4.5.

Mobile phase: Methanol and Buffer (30:70)

Standard solution: 1 mg/mL of USP Methocarbamol RS in Mobile phase

Sample solution: Nominally 1 mg/mL of methocarbamol from a suitable volume of Injection containing NLT 100 mg of methocarbamol in Mobile phase

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 274 nm

Column: 4.6-mm × 10.0-cm; 3-μm or 5-μm packing L1

Column temperature: 30°

Flow rate: 1 mL/min

Injection volume: 20 μL

System suitability

Sample: Standard solution

Suitability requirements

Relative standard deviation: NMT 2.0%

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of methocarbamol (C₁₁H₁₅NO₅) 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 Methocarbamol RS in the Standard solution (mg/mL)

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

Acceptance criteria: 95.0%–105.0%

4 IMPURITIES

Limit of Aldehydes

Diluent: Alcohol and water (20:80)

Solution A: 10 mg/mL of phenylhydrazine hydrochloride in Diluent

Solution B: 10 mg/mL of potassium ferricyanide in water

Solution C: 10 μg/mL of formaldehyde in water prepared as follows. Dissolve 1.37 g of formaldehyde solution in 1 L of water. Dilute 10 mL of the resulting solution with water to 500 mL.

Standard solution: Transfer 4 mL of Solution C to a 25-mL volumetric flask. Add 2.0 mL of filtered Solution A. Allow to stand for 10 min. Add 1mL of Solution B, and allow to stand for 5 min. Add 4 mL of hydrochloric acid, and dilute with alcohol to volume.

Sample solution: Empty the contents of NLT 10 vials of Injection to a suitable container. Transfer 4.0 mL of the composite sample of Injection to a 25-mL volumetric flask. Add 2.0 mL of filtered Solution A, and allow to stand for 10 min. Add 1 mL of Solution B, and allow to stand for 5 min. Add 4 mL of hydrochloric acid, and dilute with alcohol to volume.

Blank: Transfer 4 mL of water to a 25-mL volumetric flask. Add 2.0 mL of filtered Solution A, and allow to stand for 10 min. Add 1 mL of Solution B, and allow to stand for 5 min. Add 4 mL of hydrochloric acid, and dilute with alcohol to volume.

Instrumental conditions

Mode: Vis

Analytical wavelength: 515 nm

Cell: 1 cm

Analysis

Samples: Standard solution, Sample solution, and Blank

Determine the absorbances of the Samples.

Acceptance criteria: The absorbance of the Sample solution is NMT the absorbance of the Standard solution (NMT 10 μg of formaldehyde in each mL of Injection).

5 SPECIFIC TESTS

pH 〈791〉: 3.5–6.0

Bacterial Endotoxins Test 〈85〉: NMT 0.2 USP Endotoxin Units/mg of methocarbamol

Particulate Matter in Injections 〈788〉: Meets the requirements for small-volume injections

Other Requirements: Meets the requirements in Injections and Implanted Drug Products 〈1〉

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in single-dose containers. Store at controlled room temperature.

USP Reference Standards 〈11〉

USP Methocarbamol RS