Dexamethasone Sodium Phosphate Injection
»Dexamethasone Sodium Phosphate Injection is a sterile solution of Dexamethasone Sodium Phosphate in Water for Injection.It contains not less than 90.0percent and not more than 115.0percent of the labeled amount of dexamethasone phosphate (C22H30FO8P),present as the disodium salt.
Packaging and storage—
Preserve in single-dose or in multiple-dose containers,preferably of Type Iglass,protected from light.
Identification—
Pipet a volume of Injection,equivalent to 10mg of dexamethasone phosphate,into a 100-mLvolumetric flask,add water to volume,and mix.Pipet 5mLof this solution into a 125-mLseparator,and wash with two 10-mLportions of water-washed methylene chloride,discarding the washings.Transfer the solution into a glass-stoppered,50-mLtube,and add 5mLof alkaline phosphatase solution,prepared by dissolving 50mg of alkaline phosphatase enzyme in 50mLof pH9Buffer with magnesium(prepared as directed in Identificationtest Aunder Dexamethasone Sodium Phosphate).Allow to stand at 37
for 45minutes,and extract with 25mLof methylene chloride.Evaporate 15mLof the methylene chloride extract on a steam bath to dryness,and dissolve the residue in 1mLof methylene chloride.Apply 5µLof this solution and 5µLof a solution of USP Dexamethasone RSin methylene chloride containing 300µg per mLto a 20-×20-cm,thin-layer chromatographic plate (see Chromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel.Allow the spots to dry,and develop the chromatogram in a tank completely lined with a strip of filter paper,using a solvent system consisting of a mixture of 50parts of chloroform,50parts of acetone,and 1part of water,until the solvent front has moved about three-fourths of the length of the plate.Remove the plate from the developing tank,mark the solvent front,and allow the spots to dry.Spray the plate with dilute sulfuric acid (1in 2),and heat at 105until brown or black spots appear:the RFvalue of the principal spot obtained from the test specimen corresponds to that obtained from the Reference Standard.
for 45minutes,and extract with 25mLof methylene chloride.Evaporate 15mLof the methylene chloride extract on a steam bath to dryness,and dissolve the residue in 1mLof methylene chloride.Apply 5µLof this solution and 5µLof a solution of USP Dexamethasone RSin methylene chloride containing 300µg per mLto a 20-×20-cm,thin-layer chromatographic plate (see Chromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel.Allow the spots to dry,and develop the chromatogram in a tank completely lined with a strip of filter paper,using a solvent system consisting of a mixture of 50parts of chloroform,50parts of acetone,and 1part of water,until the solvent front has moved about three-fourths of the length of the plate.Remove the plate from the developing tank,mark the solvent front,and allow the spots to dry.Spray the plate with dilute sulfuric acid (1in 2),and heat at 105until brown or black spots appear:the RFvalue of the principal spot obtained from the test specimen corresponds to that obtained from the Reference Standard.
Bacterial endotoxins á85ñ—
It contains not more than 31.3USP Endotoxin Units per mg of dexamethasone phosphate.
pHá791ñ:
between 7.0and 8.5.
Other requirements—
It meets the requirements under Injections á1ñ.
Assay—
Mobile phase—
Prepare a suitable degassed solution of 0.01Mmonobasic potassium phosphate in a mixture of methanol and water (1:1)which,at ambient temperature and at a flow rate of about 1.6mLper minute,gives a retention time of about 5minutes for dexamethasone phosphate.
Standard preparation—
[NOTE—Prepare this solution at the time of use.]Dissolve an accurately weighed quantity of USP Dexamethasone Phosphate RSin Mobile phaseto obtain a solution having a known concentration of about 80µg per mL.
Assay preparation—
Transfer an accurately measured volume of Injection,equivalent to about 8mg of dexamethasone phosphate,to a 100-mLvolumetric flask.Dilute with Mobile phaseto volume,and mix.
Chromatographic system
(see Chromatography á621ñ)—The liquid chromatograph is equipped with a 254-nm detector and a 4-mm ×30-cm column that contains packing L1.Chromatograph five replicate injections of the Standard preparation,and record the peak responses as directed under Procedure:the relative standard deviation is not more than 1.5%.
Procedure—
By means of a suitable sampling valve,separately inject equal volumes (about 20µL)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 C22H30FO8Pin each mLof the Injection taken by the formula:
0.1(C/V)(rU/rS),
in which Cis the concentration,in µg per mL,of USP Dexamethasone Phosphate RSin the Standard preparation,Vis the volume,in mL,of Injection taken,and rUand rSare the peak responses at equivalent retention times 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 595
Phone Number:1-301-816-8139