Methocarbamol Injection
»Methocarbamol Injection is a sterile solution of Methocarbamol in an aqueous solution of Polyethylene Glycol 300.It contains not less than 95.0percent and not more than 105.0percent of the labeled amount of methocarbamol (C11H15NO5).
Packaging and storage— Preserve in single-dose containers,preferably of Type Iglass.
Identification— Mix a volume of Injection,equivalent to about 500mg of methocarbamol,with 40mLof water in a small separator.Extract with 10mLof 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 40under a stream of nitrogen to dryness:the residue so obtained meets the requirements for Identificationtest Aunder Methocarbamol.
Bacterial endotoxins á85ñ— It contains not more than 0.2USP Endotoxin Unit per mg of methocarbamol.
pHá791ñ: between 3.5and 6.0.
Particulate matter á788ñ: meets the requirements for small-volume injections.
Aldehydes— Transfer to a 25-mLvolumetric flask an accurately measured volume of Injection,equivalent to 400mg of methocarbamol,add 2.0mLof a filtered 1in 100solution of phenylhydrazine hydrochloride in dilute alcohol (1in 5),and allow to stand for 10minutes.Add 1mLof potassium ferricyanide solution (1in 100),and allow to stand for 5minutes.Add 4mLof 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 515nm,with a suitable spectrophotometer,using a reagent blank to set the instrument:the absorbance is not greater than that produced by 4mLof formaldehyde solution (1in 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 C11H15NO5as determined in the Assay.
Other requirements— It meets the requirements under Injections á1ñ.
Assay—
pH4.5Buffer solution— Dissolve 6.8g of monobasic potassium phosphate in 1000mLof water.Adjust with 18Nphosphoric acid or 10Npotassium hydroxide to a pHof 4.5±0.05.
Mobile phase— Prepare a suitable filtered and degassed solution of pH4.5Buffer solutionand methanol (about 70:30)(see System Suitabilityunder Chromatography á621ñ).
Standard preparation— Dissolve an accurately weighed quantity of USP Methocarbamol RSin Mobile phaseto obtain a solution having a known concentration of about 1mg per mL.
Assay preparation— Transfer an accurately measured volume of Injection,equivalent to 100mg of methocarbamol,to a 100-mLvolumetric flask.Dilute with Mobile phaseto volume,and mix.
Chromatographic system (see Chromatography á621ñ)—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 1mLper 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 20µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of methocarbamol (C11H15NO5)in each mLof the Injection taken by the formula:
(100C/V)(rU/rS),
in which Cis the concentration,in mg per mL,of USP Methocarbamol RSin the Standard preparation;Vis the volume,in mL,of Injection taken;and rUand rSare the peak responses of methocarbamol obtained from the Assay preparation and theStandard preparation,respectively.
Auxiliary Information— Staff Liaison:Ravi Ravichandran,Ph.D.,Senior Scientist
Expert Committee:(PA3)Pharmaceutical Analysis 3
USP28–NF23Page 1246
Phone Number:1-301-816-8330