Cyanocobalamin Co 58Capsules, chemical structure, molecular formula, Reference Standards

Cyanocobalamin Co 58Capsules

Vitamin B12-58Co

»Cyanocobalamin Co 58Capsules contain Cyanocobalamin in which a portion of the molecules contain radioactive cobalt (58Co)in the molecular structure.Each Capsule contains not less than 90.0percent and not more than 110.0percent of the labeled amount of 58Co as cyanocobalamin expressed in megabecquerels (or microcuries)at the time indicated in the labeling.The cyanocobalamin content is not less than 90.0percent and not more than 110.0percent of the labeled amount.

Specific activity: not less than 0.02MBq (or 0.5µCi)per µg of cyanocobalamin.

Packaging and storage— Preserve in well-closed,light-resistant containers,and store in a cold place.

Labeling— Label it to include the following:the date of calibration;the amount of cyanocobalamin expressed in µg per Capsule;the amount of 58Co as cyanocobalamin expressed in MBq (or µCi)per Capsule at the time of calibration;the expiration date;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 58Co is 70.9days.

USP Reference standards á11ñ— USP Cyanocobalamin RS.

Disintegration á701ñ: 30minutes,testing one Capsule in 1Nhydrochloric acid maintained at 37±2ºas the immersion fluid.

Radionuclide identification á821ñ—

A: Its gamma-ray spectrum is identical to that of a specimen of 58Co that exhibits major photopeaks at 0.511MeV(annihilation radiation)and 0.811MeV.

B: The retention time of the major peak in the radiochromatogram of the Test solutioncorresponds to that in the chromatogram of the Standard solution,as obtained in the test for Radiochemical purity.

Uniformity of dosage units á905ñ: meet the requirements.

Procedure for content uniformity— Determine the instrument response of each of 10Capsules by measurement in a suitable counting assembly and under identical geometric conditions.Calculate the average radioactivity per Capsule.The radioactivities of none of the Capsules differ by more than 10%from the average.The relative standard deviation is less than 3.5%.

Radiochemical purity—

Mobile phase— Prepare a solution of 10.0g of dibasic sodium phosphate in 1000mLof water,and adjust with phosphoric acid to a pHof 3.5.Prepare a mixture of the solution so obtained and methanol (73.5:26.5),mix,and degas.Use within 2days.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard solution— Transfer about 10mg of USP Cyanocobalamin RS,accurately weighed,to a 100-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.Transfer 2.0mLof the solution so obtained to a 100-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.

Test solution— Dissolve the contents of one Capsule in 1mLof water,allow to stand for about 10minutes,and centrifuge.Use the supernatant.

Chromatographic system(seeChromatography á621ñ)— The liquid chromatograph is equipped with a 361-nm detector,a gamma detector adjusted for 58Co,and a 4.6-mm ×25-cm stainless steel column that contains 5-µm packing L7.The flow rate is about 1mLper minute.Chromatograph the Standard solution,and record the peak responses as directed for Procedure.

Procedure— Inject about 100µLof the Standard solutioninto the chromatograph,record the chromatogram for 30minutes,and note the retention time of the cyanocobalamin peak.Inject 100µLof the Test solutioninto the chromatograph,record the chromatogram for three times the retention time of cyanocobalamin,and measure the peak areas using the gamma detector.Calculate the percentage of cyanocobalamin present as cyanocobalamin 58Co in the portion of Capsules taken by the formula:

100(rU/rs),

in which rUis the peak area for cyanocobalamin 58Coobtained from the Test solution;and rsis the sum of all the peak areas in the radiochromatogram obtained from the Test solution:not less than 90%of the total radioactivity is found as cyanocobalamin 58Co.

Radionuclidic purity— Using a suitable,calibrated instrument (see Radioactivity á821ñ)and standardized solutions of 58Co,57Co,and 60Co,record the gamma spectrum.The spectrum does not differ significantly from that of the standardized 58Co solution.Determine the relative amounts of 58Co,57Co,and 60Co present.Cobalt 57has a half-life of 270.9days,and its presence is shown by 0.122MeVgamma photons.Cobalt 60has a half-life of 5.27years and its presence is shown by 1.173MeVand 1.333MeVgamma photons.Not more than 1%of the total radioactivity is due to 60Co;and not more than 2%of the total radioactivity is due to 57Co,60Co,and other radionuclidic impurities.

Content of cyanocobalamin— Determine the content,in µg per Capsule,of cyanocobalamin as directed under Vitamin B12Activity Assay á171ñ.

Assay for radioactivity á821ñ— Using a suitable counting assembly (see Selection of a Counting Assembly)and calibrated system,determine the radioactivity,in MBq (or µCi)per Capsule,of Cyanocobalamin Co 58Capsules.

Auxiliary Information— Staff Liaison:Andrzej Wilk,Ph.D.,Senior Scientific Associate

Expert Committee:(RMI)Radiopharmaceuticals and Medical Imaging Agents

USP28–NF23Page 530

Pharmacopeial Forum:Volume No.27(6)Page 3395

Phone Number:1-301-816-8305