Samarium Sm 153Lexidronam Injection
»Samarium Sm 153Lexidronam Injection is a sterile aqueous solution suitable for intravenous injection that contains 153Sm in the form of a complex with ethylenediaminetetramethylenephosphonic acid (EDTMP).It contains not less than 90.0percent and not more than 110.0percent of the labeled amount of 153Sm expressed in megabecquerels per mL(or in millicuries per mL)at the date and time indicated in the labeling.Not less than 99percent of the Sm-153is complexed by EDTMP.It contains no antimicrobial agents.
Packaging and storage— Preserve in adequately shielded single-dose containers in a freezer.
Labeling— Label it to include the following,in addition to the information specified for Labelingunder Injections á1ñ:the time and date of calibration;the amount of 153Sm complexed with EDTMPexpressed as total megabecquerels (or millicuries)and the concentration as megabecquerels per mL(or millicuries per mL)at the time of calibration;the expiration date and time;and the statement “Caution—Radioactive Material.”The labeling indicates that in making dosage calculations,correction is to be made for radioactive decay,and also indicates that the radioactive half-life of 153Sm is 46.3hours.The labeling indicates that it should not be diluted or mixed with other solutions,that it is to be thawed at room temperature before administration,and that it is to be used within 8hours of thawing.
Radionuclide identification á821ñ— Samarium-153decays by beta emission to stable Europium 153as follows:640keV(30%),710keV(50%),and 810keV(20%).The average emission energy is 233keV.Its gamma-ray spectrum is identical to that of a specimen of known purity of 153Sm that exhibits major photopeaks having energies of 70keVand 103keV.
Bacterial endotoxins á85ñ— The limit of endotoxin content is not more than 175/VUSP Endotoxin Unit per mLof Injection,in which Vis the maximum recommended total dose,in mL,at the expiration time.
pHá791ñ: between 7.0and 8.5.
Radionuclidic purity á821ñ— Using a gamma ray spectrophotometer,determine the radionuclidic purity of the Injection:not less than 99.8%of the total radioactivity is present as Sm 153at the time of expiry.The Europium 154radioactivity is not more than 3.44kBq per 37MBq of Samarium 153(or 0.0093%of total Samarium 153at expiry).The sum of all other radionuclidic impurities is less than or equal to 0.1907%of the total Sm 153at expiry.
Radiochemical purity á821ñ—
Mobile phase— Transfer 8.0g of sodium chloride,0.2g of monobasic potassium phosphate,1.15g of dibasic sodium phosphate,and 0.2g of potassium chloride to a 1-liter volumetric flask,dilute with distilled water to volume,and mix.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).
Chromatographic system (see Chromatography á621ñ)—A10-mm ×40-mm glass chromatographic column is packed using gravity flow with a strong cation-exchange resin*(prepared by mixing 5g of resin with 25mLof water in a suitable beaker)to a final resin volume of 0.5mL.
Procedure— Transfer the packed column to an ion-chamber dose counter to determine the background count for Sm 153.Apply about 10µLof the Injection onto the column and place it in the ion-chamber counter,and record the total radioactivity.Elute the complexed radioactivity using about 20mLof Mobile phase,and record the radioactivity retained on the column.Subtract the background radioactivity from all measured radioactivity values.Calculate the percentage of complexed radioactivity in the portion of Injection taken by the formula:
100(T-S/0.95)/T,
in which Tis the total amount of radioactivity;Sis the quantity of free Sm-153retained on the column;and 0.95is the correction factor (5%of the uncomplexed Sm 153passes through the column and into the Injection):not less than 99%of the Sm-153is complexed by EDTMP.
Other requirements— It meets the requirements under Injections á1ñ,except that it is not subject to the recommendation on Volume in Container.
Assay for radioactivity á821ñ— Using a suitable counting assembly (see Gamma-Emitting Radionuclidesunder the Assay),determine the radioactivity in MBq (or mCi)per mLof Injection by use of a calibrated system:the activity is within ±10%of the labeled amount at the time of calibration.
*  Sephadex-CM C-25brand of ion exchange resin is available from Aldrich Chemical (No.27,124-1).
Auxiliary Information— Staff Liaison:Andrzej Wilk,Ph.D.,Senior Scientific Associate
Expert Committee:(RMI)Radiopharmaceuticals and Medical Imaging Agents
USP28–NF23Page 1751
Phone Number:1-301-816-8305