U.S. PHARMACOPEIA

Search USP29  
Azathioprine Sodium for Injection
» Azathioprine Sodium for Injection is a sterile solid prepared by the freeze-drying of an aqueous solution of Azathioprine and Sodium Hydroxide. It contains not less than 93.0 percent and not more than 107.0 percent of the labeled amount of azathioprine (C9H7N7O2S).
Packaging and storage— Preserve in Containers for Sterile Solids as described under Injections 1, at controlled room temperature.
Completeness of solution 641— The contents of 1 container are soluble in 10 mL of water, to give a clear, bright yellow solution, essentially free from foreign matter.
Identification— The principal spot in the chromatogram of the specimen under examination obtained in the test for Limit of mercaptopurine shows the same RF value as that obtained with the solution of USP Azathioprine RS.
Bacterial endotoxins 85— It contains not more than 1.0 USP Endotoxin Unit per mg of azathioprine.
pH 791: between 9.8 and 11.0, the contents of 1 container being dissolved in 10 mL of water.
Water, Method I 921: not more than 7.0%, the Test Preparation being prepared as directed for a hygroscopic specimen.
Limit of mercaptopurine— Prepare solutions in dimethylformamide containing, respectively, 10 mg of Azathioprine Sodium for Injection per mL, 10 mg of USP Azathioprine RS per mL, and 100 µg of USP Mercaptopurine RS per mL. Apply 15 µL of the USP Mercaptopurine RS solution and 5-µL portions of the other two solutions at points about 2 cm from the bottom edge of a thin-layer chromatographic plate (see Chromatography 621) coated with a 250-µm layer of microcrystalline cellulose. Allow the spots to dry, and develop the chromatogram in a suitable chamber, using butyl alcohol, previously saturated with 5 N ammonium hydroxide, as the solvent, until the solvent front has moved about 15 cm from the point of application. Remove the plate, air-dry, and locate the spots by viewing under short- and long-wavelength UV light: any spot in the chromatogram from azathioprine, other than the principal spot, is not more intense than the spot in the chromatogram obtained with USP Mercaptopurine RS (3.0%).
Residual solvents 467: meets the requirements.
(Official January 1, 2007)
Other requirements— It meets the requirements under Injections 1 and Uniformity of Dosage Units 905.
Assay—
Standard preparation— Transfer 25 mg of USP Azathioprine RS, accurately weighed, to a 50-mL volumetric flask, dissolve in 2.5 mL of 0.1 N sodium hydroxide, dilute with water to volume, and mix. Pipet 10.0 mL of this solution into a 50-mL volumetric flask, dilute with 0.1 N sulfuric acid to volume, and mix.
Assay preparation— Transfer the contents of 1 vial of Azathioprine Sodium for Injection with the aid of water to a 100-mL volumetric flask, dilute with water to volume, and mix. Pipet 10 mL of this solution into another 100-mL volumetric flask, dilute with 0.1 N sulfuric acid to volume, and mix.
Procedure— Transfer 20 mL each of the Standard preparation and the Assay preparation, separately, to polarographic cells, and deaerate for 10 minutes with nitrogen that previously has been saturated with 0.1 N sulfuric acid. Blanket the solution with saturated nitrogen, insert the dropping mercury electrode of a suitable polarograph, and record the polarogram from 0.60 volt to 1.00 volt, using a saturated calomel electrode as the reference electrode. Determine the height of the diffusion current as the difference between the residual current and diffusion current plateau. Calculate the quantity, in mg, of azathioprine (C9H7N7O2S) in the volume of solution from the vial used for the Assay preparation taken by the formula:
0.1C(id)U / (id)S,
in which C is the concentration, in µg per mL, of USP Azathioprine RS in the Standard preparation; and (id)U and (id)S are the diffusion currents of the Assay preparation and the Standard preparation, respectively.
Auxiliary Information— Staff Liaison : Feiwen Mao, M.S., Senior Scientific Associate
Expert Committee : (MDOOD05) Monograph Development-Ophthalmics Oncologics and Dermatologicals
USP29–NF24 Page 226
Phone Number : 1-301-816-8320