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 90.0 percent and not more than 115.0 percent of the labeled amount of dexamethasone phosphate (C22H30FO8P), present as the disodium salt.
Packaging and storage Preserve in single-dose or multiple-dose containers, preferably of Type I glass, protected from light.
USP Reference standards 11
USP Endotoxin RS
Identification Pipet a volume of Injection, equivalent to 10 mg of dexamethasone phosphate, into a 100-mL volumetric flask, add water to volume, and mix. Pipet 5 mL of this solution into a 125-mL separator, and wash with two 10-mL portions of water-washed methylene chloride, discarding the washings. Transfer the solution into a glass-stoppered, 50-mL tube, and add 5 mL of alkaline phosphatase solution, prepared by dissolving 50 mg of alkaline phosphatase enzyme in 50 mL of pH 9 Buffer with magnesium (prepared as directed in Identification test A under Dexamethasone Sodium Phosphate). Allow to stand at 37 for 45 minutes, and extract with 25 mL of methylene chloride. Evaporate 15 mL of the methylene chloride extract on a steam bath to dryness, and dissolve the residue in 1 mL of methylene chloride. Apply 5 µL of this solution and 5 µL of a solution of USP Dexamethasone RS in methylene chloride containing 300 µg per mL to a 20- × 20-cm, thin-layer chromatographic plate (see Chromatography 621) 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 50 parts of chloroform, 50 parts of acetone, and 1 part 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 (1 in 2), and heat at 105 until brown or black spots appear: the RF value of the principal spot obtained from the test specimen corresponds to that obtained from the Reference Standard.
Bacterial endotoxins 85 It contains not more than 31.3 USP Endotoxin Units per mg of dexamethasone phosphate.
pH 791: between 7.0 and 8.5.
Other requirements It meets the requirements under Injections 1.
Mobile phase Prepare a suitable degassed solution of 0.01 M monobasic potassium phosphate in a mixture of methanol and water (1:1) which, at ambient temperature and at a flow rate of about 1.6 mL per minute, gives a retention time of about 5 minutes for dexamethasone phosphate.
Standard preparation [notePrepare this solution at the time of use. ] Dissolve an accurately weighed quantity of USP Dexamethasone Phosphate RS in Mobile phase to obtain a solution having a known concentration of about 80 µg per mL.
Assay preparation Transfer an accurately measured volume of Injection, equivalent to about 8 mg of dexamethasone phosphate, to a 100-mL volumetric flask. Dilute with Mobile phase to volume, and mix.
Chromatographic system (see Chromatography 621)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 20 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of C22H30FO8P in each mL of the Injection taken by the formula:
0.1(C / V)(rU / rS)in which C is the concentration, in µg per mL, of USP Dexamethasone Phosphate RS in the Standard preparation, V is the volume, in mL, of Injection taken, and rU and rS are the peak responses at equivalent retention times obtained from the Assay preparation and the Standard preparation, respectively.
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USP35NF30 Page 2845