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C18H25NO 271.4

Morphinan, 3-methoxy-17-methyl-, (9,13,14)-.
3-Methoxy-17-methyl-9,13,14-morphinan [125-71-3].
» Dextromethorphan contains not less than 98.0 percent and not more than 101.0 percent of C18H25NO, calculated on the anhydrous basis.
Packaging and storage— Preserve in tight containers.
Solution: 100 µg per mL.
Medium: dilute hydrochloric acid (1 in 120).
Absorptivities at 278 nm, calculated on the anhydrous basis, do not differ by more than 3.0%.
Melting range, Class I 741: between 109.5 and 112.5.
Specific rotation 781S
Test solution: 100 mg per mL, in chloroform. Its specific rotation does not differ from that of the similarly prepared solution of USP Dextromethorphan RS by more than 1.0%.
Water, Method Ia 921: not more than 0.5%.
Residue on ignition 281: not more than 0.1%.
Limit of N,N-dimethylaniline—
Standard solution— Transfer about 50 mg of N,N-dimethylaniline to a 100-mL volumetric flask, add 70.0 mL of water, insert the stopper tightly, shake for 20 minutes using a mechanical wrist-action shaker or equivalent, dilute with water to volume, and mix. Transfer 1.0 mL to a 100-mL volumetric flask, dilute with water to volume, transfer 1.0 mL of this solution to a 25-mL volumetric flask, and add 19 mL of water.
Test solution— Transfer about 500 mg of Dextromethorphan, accurately weighed, to a 25-mL volumetric flask, add 19 mL of water and 1 mL of 3 N hydrochloric acid, dissolve by warming on a steam bath, and cool.
Procedure— Add 2 mL of 1 N acetic acid and 1 mL of sodium nitrite solution (1 in 100) to the Test solution, dilute with water to volume, and mix. This solution shows no more color than the straw yellow to greenish yellow color of the solution obtained from the Standard solution similarly treated: not more than 0.001% of N,N-dimethylaniline is found.
Limit of phenolic compounds— Dissolve about 10 mg in 2 mL of 3 N hydrochloric acid, and add 2 drops of ferric chloride TS. Mix, add 2 drops of potassium ferricyanide TS, and observe after 2 minutes: no blue-green color develops.
Assay— Dissolve about 700 mg of Dextromethorphan, accurately weighed, in 60 mL of glacial acetic acid, warming slightly, if necessary, to dissolve. Add 2 drops of crystal violet TS, and titrate with 0.1 N perchloric acid VS to a blue-green endpoint. Perform a blank determination, and make any necessary correction. Each mL of 0.1 N perchloric acid is equivalent to 27.14 mg of C18H25NO.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Clydewyn M. Anthony, Ph.D.
(MDCCA05) Monograph Development-Cough Cold and Analgesics
Reference Standards Lili Wang, Technical Services Scientist
USP32–NF27 Page 2105