Add the following:

FOR ORAL SUSPENSION PACKAGED IN SINGLE-UNIT CONTAINERS: meets the requirements.USP28

Add the following:

FOR ORAL SUSPENSION PACKAGED IN MULTIPLE-UNIT CONTAINERS: meets the requirements.USP28

Diethylamine phosphate buffer,Diluent,Mobile phase,Standard preparation,and Chromatographic system— Proceed as directed in the Assayunder Propoxyphene Napsylate Tablets.

Assay preparation— Transfer an accurately weighed quantity of the well-mixed Oral Suspension,equivalent to about 50mg of propoxyphene napsylate monohydrate,to a 100-mLvolumetric flask.Dissolve in and dilute with a solution of acetonitrile in water (2in 5)to volume,and mix.Further dilute 10.0mLof the resulting solution to 50mLwith the solution of acetonitrile in water (2in 5).

Procedure— Separately inject equal volumes (about 20µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the areas for the propoxyphene peaks.Calculate the quantity,in mg,of propoxyphene napsylate (C22H29NO2·C10H8O3S·H2O)in each mLof the Oral Suspension taken by the formula: in which 565.72and 547.72are the molecular weights of propoxyphene napsylate and anhydrous propoxyphene napsylate,respectively;Cis the concentration,in mg per mL,of anhydrous USP Propoxyphene Napsylate RSin the Standard preparation;Dis the density,in g per mL,of the Oral Suspension;WUis the weight,in g,of the Oral Suspension taken;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.