A: The retention times of the carbinoxamine maleate and dextromethorphan hydrobromide peaks in the chromatogram of the Assay preparation correspond to those in the chromatogram of the Standard preparation, as obtained in the Assay for carbinoxamine maleate and dextromethorphan hydrobromide.

B: The retention time of the pseudoephedrine hydrochloride peak in the chromatogram of the Assay preparation corresponds to that in the chromatogram of the Standard preparation, as obtained in the Assay for pseudoephedrine hydrochloride.

FOR ORAL SOLUTION PACKAGED IN SINGLE-UNIT CONTAINERS: meets the requirements.

FOR ORAL SOLUTION PACKAGED IN MULTIPLE-UNIT CONTAINERS: meets the requirements.

(Official January 1, 2007)

pH 5.5 buffer— Dissolve about 4.4 g of dibasic potassium phosphate in 1000 mL of water. Adjust with phosphoric acid to a pH of 5.5.

Mobile phase— Prepare a filtered and degassed mixture of methanol and pH 5.5 buffer (60:40). Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard preparation— Dissolve accurately weighed quantities of USP Carbinoxamine Maleate RS and USP Dextromethorphan Hydrobromide RS in water, and dilute quantitatively, and stepwise if necessary, with water to obtain a solution having known concentrations of about 0.1 mg per mL of carbinoxamine maleate and 0.3 mg per mL of dextromethorphan hydrobromide.

Assay preparation— Transfer an accurately measured volume of Oral Solution to a volumetric flask, and dilute with water to volume to obtain a solution having concentrations of about 0.1 mg per mL of carbinoxamine maleate and 0.3 mg per mL of dextromethorphan hydrobromide, and mix.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 225-nm detector and a 4.6-mm × 25-cm column that contains packing L9. The flow rate is about 1.5 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the relative retention times are about 0.8 for dextromethorphan and 1.0 for carbinoxamine; the resolution, R, between carbinoxamine and dextromethorphan is not less than 3.0; the tailing factor for the dextromethorphan peak is not more than 2.0; and the relative standard deviation for replicate injections 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 analyte peaks. Calculate the quantities, in mg, of carbinoxamine maleate (C16H19ClN2O·C4H4O4) and dextromethorphan hydrobromide (C18H25NO·HBr) in each mL in the volume of Oral Solution taken by the formula: in which C is the concentration, in mg per mL, of the appropriate Reference Standard in the Standard preparation; V is the volume of Oral Solution taken; D is the dilution factor used for the Assay preparation; and rU and rS are the peak responses for the appropriate analyte obtained from the Assay preparation and the Standard preparation, respectively.

pH 5.5 buffer and Mobile phase— Proceed as directed in the Assay for carbinoxamine maleate and dextromethorphan hydrobromide.

Standard preparation— Dissolve an accurately weighed quantity of USP Pseudoephedrine Hydrochloride RS in water, and dilute quantitatively, and stepwise if necessary, with water to obtain a solution having a known concentration of about of 1.2 mg per mL of pseudoephedrine hydrochloride.

Assay preparation— Transfer an accurately measured volume of Oral Solution to a volumetric flask, dilute with water to volume to obtain a solution having a concentration of about 1.2 mg per mL of pseudoephedrine hydrochloride, and mix.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 257-nm detector and a 4.6-mm × 25-cm column that contains packing L9. The flow rate is about 1.5 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the column efficiency is not less than 1000 theoretical plates; and the relative standard deviation for replicate injections 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 analyte peaks. Calculate the quantity, in mg, of pseudoephedrine hydrochloride (C10H15NO·HCl) in each mL in the volume of Oral Solution taken by the formula: in which C is the concentration, in mg per mL, of USP Pseudoephedrine Hydrochloride RS in the Standard preparation; V is the volume of Oral Solution taken; D is the dilution factor used for the Assay preparation; and rU and rS are the peak responses for pseudoephedrine hydrochloride obtained from the Assay preparation and the Standard preparation, respectively.