Dextromethorphan Hydrobromide
C18H25NO·HBr·H2O 370.32

Morphinan,3-methoxy-17-methyl-,(9a,13a,14a)-,hydrobromide,monohydrate.
3-Methoxy-17-methyl-9a,13a,14a-morphinan hydrobromide monohydrate [6700-34-1].

Anhydrous 352.32 [125-69-9].
»Dextromethorphan Hydrobromide contains not less than 98.0percent and not more than 102.0percent of C18H25NO·HBr,calculated on the anhydrous basis.
Packaging and storage— Preserve in tight containers.
Identification—
A: Infrared Absorption á197Kñ—
Test specimen— Dry in vacuum over phosphorus pentoxide for 4hours.
B: Ultraviolet Absorption á197Uñ—
Solution: 100µg per mL.
Medium: 0.1Nhydrochloric acid.
Absorptivities at 278nm,calculated on the anhydrous basis,do not differ by more than 3.0%.
C: To 5mLof a solution (1in 200)add 5drops of 2Nnitric acid and 2mLof silver nitrate TS:a yellowish white precipitate is formed.
Specific rotation á781Sñ—
Test solution: 18mg per mL(warm it,if necessary,to dissolve).Its specific rotation,determined photoelectrically at 325nm,does not differ from that of the similarly prepared solution of USP Dextromethorphan Hydrobromide RSby more than 1.0%.
pHá791ñ: between 5.2and 6.5in a solution (1in 100).
Water,Method Iá921ñ: between 3.5%and 5.5%.
Residue on ignition á281ñ: not more than 0.1%.
Limit of N,N-dimethylaniline— Proceed as directed in the test for Limit of N,N-dimethylanilineunder Dextromethorphan,except to use Dextromethorphan Hydrobromide.
Limit of phenolic compounds— To about 5mg add 1drop of 3Nhydrochloric acid,1mLof water,and 2drops of ferric chloride TS.Mix,add 2drops of potassium ferricyanide TS,and observe after 2minutes:no blue-green color develops.
Assay—
Mobile phase— Prepare a filtered and degassed solution containing 0.007Mdocusate sodium and 0.007Mammonium nitrate in a mixture of acetonitrile and water (70:30),and adjust the solution with glacial acetic acid to a pHof 3.4.[NOTE—Dissolve the docusate sodium in the acetonitrile and water mixture before adding the ammonium nitrate.]
Standard preparation— Dissolve an accurately weighed quantity of USP Dextromethorphan Hydrobromide RSin water to obtain a stock solution having a known concentration of about 1mg per mL.Transfer 10.0mLof this solution to a 100-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.
Assay preparation— Transfer about 100mg of Dextromethorphan Hydrobromide,accurately weighed,to a 100-mLvolumetric flask,add water to volume,and mix.Transfer 10.0mLof this solution to a 100-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.
Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 280-nm detector and a 4.6-mm ×25-cm column that contains 5-µm packing L1.The flow rate is about 1mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the tailing factor for the major peak is not more than 2.5;and the relative standard deviation 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 C18H25NO·HBr in the portion of Dextromethorphan Hydrobromide taken by the formula:
1000C(rU/rS),
in which Cis the concentration,in mg per mL,of USP Dextromethorphan Hydrobromide RSin the Standard preparation;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.
Auxiliary Information— Staff Liaison:Clydewyn M.Anthony,Ph.D.,Scientist
Expert Committee:(PA2)Pharmaceutical Analysis 2
USP28–NF23Page 610
Phone Number:1-301-816-8139
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