Cephalexin Capsules
»Cephalexin Capsules contain the equivalent of not less than 90.0percent and not more than 120.0percent of the labeled amount of C16H17N3O4S.
Packaging and storage— Preserve in tight containers.
Identification— Mix the contents of 1Capsule with water to obtain a concentration of about 3mg of cephalexin per mL,and filter (test solution).Place a suitable thin-layer chromatographic plate (see Chromatography á621ñ)coated with a 0.25-mm layer of binder-free silica gel in a chamber containing a mixture of n-hexane and tetradecane (95:5)to a depth of about 1cm,allow the solvent front to move the length of the plate,remove the plate from the chamber,and allow the solvent to evaporate.On this plate apply 10µLeach of the test solution and a Standard solution containing 3mg of USP Cephalexin RSper mL.Allow the spots to dry,and develop the chromatogram in a solvent system consisting of a mixture of 0.1Mcitric acid,0.1Mdibasic sodium phosphate,and a 1in 15solution of ninhydrin in acetone (60:40:1.5)until the solvent front has moved about three-fourths of the length of the plate.Remove the plate from the developing chamber,mark the solvent front,dry the plate for 10minutes at 110,and examine the chromatogram:the RFvalue of the principal spot obtained from the test solution corresponds to that obtained from the Standard solution.
Dissolution á711ñ—
Medium: water;900mL.
Apparatus 1: 100rpm.
Time: 30minutes.
Procedure— Determine the amount of C16H17N3O4Sdissolved from the UVabsorbances at the wavelength of maximum absorbance at about 262nm of a filtered portion of the solution under test,suitably diluted with Dissolution Medium,if necessary,to a concentration of about 20µg per mL,in comparison with a Standard solution having a known concentration of USP Cephalexin RSin the same medium.
Tolerances— Not less than 80%(Q)of the labeled amount of C16H17N3O4Sis dissolved in 30minutes.
Uniformity of dosage units á905ñ: meet the requirements.
Water,Method Iá921ñ: not more than 10.0%.
Assay—
Mobile phase ,Internal standard solution,Standard preparation,and Chromatographic system—Prepare as directed in the Assayunder Cephalexin.
Assay preparation— Remove,as completely as possible,the contents of not less than 20Capsules,and weigh accurately.Mix the combined contents,and transfer an accurately weighed quantity,equivalent to about 500mg of cephalexin,to a 500-mLvolumetric flask,add water to volume,and mix.Sonicate,if necessary,to assure complete dissolution of the cephalexin.Filter,if necessary,to obtain a clear solution.Transfer 10.0mLof this solution to a 50-mL,glass-stoppered flask,add 15.0mLof Internal standard solution,mix,and filter.
Procedure— Proceed as directed for Procedurein the Assayunder Cephalexin.Calculate the quantity,in mg,of C16H17N3O4Sin the portion of Capsules taken by the formula:
0.5CP(RU/RS),
in which the terms are as defined therein.
Auxiliary Information— Staff Liaison:William W.Wright,Ph.D.,Scientific Fellow
Expert Committee:(PA7)Pharmaceutical Analysis 7
USP28–NF23Page 414
Phone Number:1-301-816-8335