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C16H13N3O3 295.29

Carbamic acid, (5-benzoyl-1H-benzimidazol-2-yl), methyl ester.
Methyl 5-benzoyl-2-benzimidazolecarbamate [31431-39-7].
» Mebendazole contains not less than 98.0 percent and not more than 102.0 percent of C16H13N3O3, calculated on the dried basis.
Packaging and storage— Preserve in well-closed containers.
Identification, Infrared Absorption 197K.
Loss on drying 731 Dry it at 105 for 4 hours: it loses not more than 0.5% of its weight.
Residue on ignition 281: not more than 0.1%.
Chromatographic purity— Dissolve 50 mg in 1.0 mL of 96 percent formic acid in a 10-mL volumetric flask, add chloroform to volume, and mix. Similarly prepare a solution of USP Mebendazole RS in the same medium having a concentration of 5 mg per mL. Transfer 1.0 mL of this Standard solution to a 200-mL volumetric flask, add a mixture of chloroform and 96 percent formic acid (9:1) to volume, and mix (diluted Standard solution). Apply 10-µL portions of the test solution, the Standard solution, and the diluted Standard solution to a suitable thin-layer chromatographic plate (see Chromatography 621) coated with a 0.25-mm layer of chromatographic silica gel mixture. Allow the spots to dry, and develop the chromatogram in a solvent system consisting of a mixture of chloroform, methanol, and 96 percent formic acid (90:5:5) 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, allow the solvent to evaporate, and examine the plate under short-wavelength UV light: the RF value of the principal spot obtained from the test solution corresponds to that obtained from the Standard solution, and no spot, other than the principal spot, in the chromatogram of the test solution is larger or more intense than the principal spot obtained from the diluted Standard solution.
Assay— Dissolve about 225 mg of Mebendazole, accurately weighed, in 30 mL of glacial acetic acid. Titrate with 0.1 N perchloric acid VS, determining the endpoint potentiometrically, using a calomel-glass electrode system. Perform a blank determination, and make any necessary correction. Each mL of 0.1 N perchloric acid is equivalent to 29.53 mg of C16H13N3O3.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Behnam Davani, Ph.D., M.B.A.
Senior Scientist
(MDAA05) Monograph Development-Antivirals and Antimicrobials
Reference Standards Lili Wang, Technical Services Scientist
USP32–NF27 Page 2852