Dextromethorphan Hydrobromide Oral Solution

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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Dextromethorphan Hydrobromide Oral Solution contains not less than 90.0 percent and not more than 110.0 percent of the labeled amount of dextromethorphan hydrobromide (C₁₈H₂₅NO . HBr . H₂O). 

1 Packaging and storage—

Preserve in tight, light-resistant containers. 

1.1 USP Reference standards 〈11〉— 

USP Dextromethorphan Hydrobromide RS 

2 Identication— 

A: Transfer about 50 mL of Oral Solution to a 250-mL separator, add 20 mL of water, 5 mL of 2.5 N sodium hydroxide, and 40 mL of solvent hexane, and shake thoroughly. Remove the solvent hexane layer, and lter through anhydrous sodium sulfate into a 150-mL beaker. Repeat the solvent hexane extraction, using two 40-mL portions and collecting the extracts in the beaker after ltering. Evaporate the combined extracts at 50° under nitrogen to dryness, and dissolve the residue in, and dilute with, 10 mL of chloroform: the solution is dextrorotatory (see Optical Rotation 〈781〉). Retain the chloroform solution for Identication test B. 

B: Evaporate the chloroform solution from Identication test A on a steam bath to dryness, dissolve the residue in 2 mL of 2 N sulfuric acid, and add 1 mL of a freshly prepared solution of mercuric nitrate (prepared by dissolving 700 mg of mercuric nitrate in 4 mL of water, adding 100 mg of sodium nitrate, mixing, and ltering): no red color is produced immediately, but after heating, a yellow to red color develops in about 15 minutes. 

2.1 Uniformity of dosage units 〈905〉— 

for oral solution packaged in single-unit containers: meets the requirements. 

2.2 Deliverable volume 〈698〉— 

for oral solution packaged in multiple-unit containers: meets the requirements. 

3 Assay— 

Mobile phase and Standard preparation—Prepare as directed in the Assay under Dextromethorphan Hydrobromide. 

Assay preparation—Pipet, using a to-contain pipet, a volume of Oral Solution, equivalent to about 10 mg of dextromethorphan hydrobromide, into a 100-mL volumetric ask, dilute with water to volume, and mix. 

Change to read: 

Chromatographic system and Procedure (see Chromatography 〈621〉)—Proceed as directed in the Assay under Dextromethorphan Hydrobromide. Calculate the quantity, in mg, of dextromethorphan hydrobromide (C₁₈H₂₅NO . HBr . H₂O) in the volume of Oral Solution taken by the formula: 

(370.32/352.32)(100C)(r_u/r_s) 

in which 370.32 and 352.32 are the molecular weights of dextromethorphan hydrobromide and anhydrous dextromethorphan hydrobromide, respectively; C is the concentration, in mg per mL, of USP Dextromethorphan Hydrobromide RS (ERR 1-Sep-2023) in the Standard preparation; and r_u and r_s are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.