» Methocarbamol Injection is a sterile solution of Methocarbamol in an aqueous solution of Polyethylene Glycol 300. It contains not less than 95.0 percent and not more than 105.0 percent of the labeled amount of methocarbamol (C11H15NO5).
Packaging and storage Preserve in single-dose containers, preferably of Type I glass.
USP Reference standards 11
USP Endotoxin RS
Identification Mix a volume of Injection, equivalent to about 500 mg of methocarbamol, with 40 mL of water 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: the residue so obtained meets the requirements for Identification test A under Methocarbamol.
Bacterial endotoxins 85 It contains not more than 0.2 USP Endotoxin Unit per mg of methocarbamol.
pH 791: between 3.5 and 6.0.
Particulate matter 788: meets the requirements for small-volume injections.
Aldehydes Transfer to a 25-mL volumetric flask an accurately measured volume of Injection, equivalent to 400 mg of methocarbamol, add 2.0 mL of a filtered 1 in 100 solution of phenylhydrazine hydrochloride in dilute alcohol (1 in 5), and allow to stand for 10 minutes. Add 1 mL of potassium ferricyanide solution (1 in 100), and allow to stand for 5 minutes. Add 4 mL of hydrochloric acid, dilute with alcohol to volume, and mix. Determine the absorbance of this solution in a 1-cm cell at the wavelength of maximum absorbance at about 515 nm, with a suitable spectrophotometer, using a reagent blank to set the instrument: the absorbance is not greater than that produced by 4 mL of formaldehyde solution (1 in 100,000), treated in the same manner as the portion of Injection taken and similarly measured, corresponding to not more than 0.01%, as formaldehyde, based upon the content of C11H15NO5 as determined in the Assay.
Other requirements It meets the requirements under Injections 1.
pH 4.5 Buffer solution Dissolve 6.8 g of monobasic potassium phosphate in 1000 mL of water. Adjust with 18 N phosphoric acid or 10 N potassium hydroxide to a pH of 4.5 ± 0.05.
Mobile phase Prepare a suitable filtered and degassed solution of pH 4.5 Buffer solution and methanol (about 70:30) (see System Suitability under Chromatography 621).
Standard preparation Dissolve an accurately weighed quantity of USP Methocarbamol RS in Mobile phase to obtain a solution having a known concentration of about 1 mg per mL.
Assay preparation Transfer an accurately measured volume of Injection, equivalent to 100 mg of methocarbamol, to a 100-mL volumetric flask. Dilute with Mobile phase to volume, and mix.
Chromatographic system (see Chromatography 621)The liquid chromatograph is equipped with a 274-nm detector and a 4.6-mm × 10-cm column that contains 3- or 5-µm packing L1, operated at 30. The flow rate is 1 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the relative standard deviation for replicate injections is not more than 2.0%.
Procedure Separately inject equal volumes (about 20 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of methocarbamol (C11H15NO5) in each mL of the Injection taken by the formula:
(100C/V)(rU / rS)in which C is the concentration, in mg per mL, of USP Methocarbamol RS in the Standard preparation; V is the volume, in mL, of Injection taken; and rU and rS are the peak responses of methocarbamol obtained from the Assay preparation and the Standard preparation, respectively.
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USP35NF30 Page 3852