Dextromethorphan Hydrobromide
(dex'' troe meth or' fan hye'' droe broe' mide).
C18H25NO·HBr·H2O 370.32

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

Anhydrous 352.32 [125-69-9].
» Dextromethorphan Hydrobromide contains not less than 98.0 percent and not more than 102.0 percent of C18H25NO·HBr, calculated on the anhydrous basis.
Packaging and storage— Preserve in tight containers.
USP Reference standards 11
USP Dextromethorphan Hydrobromide RS Click to View Structure
Test specimen— Dry in vacuum over phosphorus pentoxide for 4 hours.
B: Ultraviolet Absorption 197U
Solution: 100 µg per mL.
Medium: 0.1 N hydrochloric acid.
Absorptivities at 278 nm, calculated on the anhydrous basis, do not differ by more than 3.0%.
C: To 5 mL of a solution (1 in 200) add 5 drops of 2 N nitric acid and 2 mL of silver nitrate TS: a yellowish white precipitate is formed.
Specific rotation 781S
Test solution: 18 mg per mL (warm it, if necessary, to dissolve). Its specific rotation, determined photoelectrically at 325 nm, does not differ from that of the similarly prepared solution of USP Dextromethorphan Hydrobromide RS by more than 1.0%.
pH 791: between 5.2 and 6.5 in a solution (1 in 100).
Water, Method I 921: between 3.5% and 5.5%.
Residue on ignition 281: not more than 0.1%.
Limit of N,N-dimethylaniline Proceed as directed in the test for Limit of N,N-dimethylaniline under Dextromethorphan, except to use Dextromethorphan Hydrobromide.
Limit of phenolic compounds— To about 5 mg add 1 drop of 3 N hydrochloric acid, 1 mL of water, and 2 drops of ferric chloride TS. Mix, add 2 drops of potassium ferricyanide TS, and observe after 2 minutes: no blue-green color develops.
Mobile phase— Prepare a filtered and degassed solution containing 0.007 M docusate sodium and 0.007 M ammonium nitrate in a mixture of acetonitrile and water (70:30), and adjust the solution with glacial acetic acid to a pH of 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 RS in water to obtain a stock solution having a known concentration of about 1 mg per mL. Transfer 10.0 mL of this solution to a 100-mL volumetric flask, dilute with Mobile phase to volume, and mix.
Assay preparation— Transfer about 100 mg of Dextromethorphan Hydrobromide, accurately weighed, to a 100-mL volumetric flask, add water to volume, and mix. Transfer 10.0 mL of this solution 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 280-nm detector and a 4.6-mm × 25-cm column that contains 5-µm packing L1. The flow rate is about 1 mL per 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 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 C18H25NO· HBr in the portion of Dextromethorphan Hydrobromide taken by the formula:
1000C(rU / rS)
in which C is the concentration, in mg per mL, of USP Dextromethorphan Hydrobromide RS in the Standard preparation; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.
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Monograph Clydewyn M. Anthony, Ph.D.
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(SM22010) Monographs - Small Molecules 2
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