Dexamethasone Elixir
»Dexamethasone Elixir contains not less than 90.0percent and not more than 110.0percent of the labeled amount of C22H29FO5.
Packaging and storage— Preserve in tight containers.
Identification— Evaporate 9mLof the Assay preparation,prepared as directed in the Assay,on a steam bath just to dryness,and dissolve the residue in 2mLof a mixture of methylene chloride and methanol (1:1).Apply separately 5µLof this solution and 5µLof a solution of Dexamethasone RSin the mixture of methylene chloride and methanol (1:1),containing 0.5mg per mL,to a thin-layer chromatographic plate coated with a 0.25-mm layer of chromatographic silica gel mixture (see Chromatography á621ñ).Allow the spots to dry,and develop the chromatogram in a solvent system consisting of a mixture of chloroform,acetone,and glacial acetic acid (80:40:1)until the solvent front has moved about three-fourths of the length of the plate.Remove the plate from the developing chamber,mark the solvent front,and allow the solvent to evaporate.Locate the spots by viewing under short-wavelength UVlight:the RFvalue of the principal spot obtained from the solution under test corresponds to that obtained from the Standard solution.
Alcohol content,Method IIá611ñ: between 3.8%and 5.7%of C2H5OH,n-propyl alcohol being used as the internal standard.
Assay—
Mobile phase— Prepare a filtered and degassed mixture of water and acetonitrile (2:1).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).
Standard preparation— Dissolve an accurately weighed quantity of USP Dexamethasone RSin dilute methanol (1in 2),and dilute quantitatively,and stepwise if necessary,with dilute methanol (1in 2)to obtain a solution having a known concentration of about 0.1mg per mL.
Assay preparation— Transfer an accurately measured volume of Elixir,freshly mixed and free from air bubbles,equivalent to about 1mg of dexamethasone,to a 10-mLvolumetric flask,dilute with water to volume,mix,and filter through a suitable membrane filter.
Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm ×30-cm column that contains packing L1.The flow rate is about 1.5mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed under Procedure:the relative standard deviation for replicate injections is not more than 3.0%.
Procedure— Separately inject equal volumes (between 5µLand 25µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of C22H29FO5in each mLof the Elixir taken by the formula:
10(C/V)(rU/rS),
in which Cis the concentration,in mg per mL,of USP Dexamethasone RSin the Standard preparation,Vis the volume,in mL,of Elixir taken,and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.
Auxiliary Information— Staff Liaison:Clydewyn M.Anthony,Ph.D.,Scientist
Expert Committee:(PA1)Pharmaceutical Analysis 1
USP28–NF23Page 588
Phone Number:1-301-816-8139