Trimethobenzamide Hydrochloride Capsules »Trimethobenzamide Hydrochloride Capsules contain not less than 90.0percent and not more than 110.0percent of the labeled amount of C21H28N2O5·HCl. Packaging and storage— Preserve in well-closed containers. USP Reference standards á11ñ USP Trimethobenzamide Hydrochloride RS. Identification— A: The UVabsorption spectrum of the solution employed for measurement of absorbance in the Assayexhibits maxima and minima at the same wavelengths as that of the Standard solution. B: Transfer a portion of the contents of Capsules,equivalent to about 20mg of trimethobenzamide hydrochloride,to a suitable vessel,dissolve in 15mLof 0.1Nhydrochloric acid,and filter.Transfer the filtrate to a separator,and add 5mLof 1Nsodium hydroxide.Extract with 15mLof chloroform,filtering the chloroform extract through anhydrous sodium sulfate into a suitable vessel,and evaporate to dryness.Allow to cool to room temperature,add a small portion of ether,and evaporate at room temperature to dryness.Dry the residue at 60for 1hour:the IRabsorption spectrum of a potassium bromide dispersion of the residue so obtained exhibits maxima only at the same wavelengths as that of a similar preparation of USP Trimethobenzamide Hydrochloride RS. C: Place a portion of the contents of Capsules,equivalent to about 25mg of trimethobenzamide hydrochloride,in a 10-mLvolumetric flask,add methanol to volume,mix,and filter:the filtrate so obtained responds to the Thin-layer Chromatographic Identification Test á201ñ,a solvent system consisting of a mixture of ethyl acetate,alcohol,and ammonium hydroxide (90:10:5)being used. Dissolution á711ñ Medium: water;900mL. Apparatus 1: 100rpm. Time: 45minutes. Procedure— Determine the amount of C21H28N2O5·HCl dissolved from UVabsorbances at the wavelength of maximum absorbance at about 258nm of filtered portions of the solution under test,suitably diluted with Medium,if necessary,in comparison with a Standard solution having a known concentration of USP Trimethobenzamide Hydrochloride RSin the same Medium. Tolerances— Not less than 75%(Q)of the labeled amount of C21H28N2O5·HCl is dissolved in 45minutes. Uniformity of dosage units á905ñ: meet the requirements. Assay— Transfer,as completely as possible,the contents of not less than 20Capsules to a suitable tared container,and determine the average weight per Capsule.Mix the combined contents,and transfer an accurately weighed portion of the powder,equivalent to about 50mg of trimethobenzamide hydrochloride,to a 100-mLvolumetric flask.Add 50mLof dilute hydrochloric acid (1in 120),shake the mixture for several minutes,then add dilute hydrochloric acid (1in 120)to volume,and mix.Filter through small retentive filter paper,discarding the first 20mLof the filtrate.Transfer 4.0mLof the subsequent filtrate to a 100-mLvolumetric flask,add dilute hydrochloric acid (1in 120)to volume,and mix.Concomitantly determine the absorbances of this solution and a Standard solution of USP Trimethobenzamide Hydrochloride RSin the same medium having a known concentration of about 20µg per mL,in 1-cm cells at the wavelength of maximum absorbance at about 258nm,with a suitable spectrophotometer,using dilute hydrochloric acid (1in 120)as the blank.Calculate the quantity,in mg,of C21H28N2O5·HCl in the portion of Capsules taken by the formula: 2.5C(AU/AS), in which Cis the concentration,in µg per mL,of USP Trimethobenzamide RSin the Standard solution,and AUand ASare the absorbances of the solution from the Capsules and the Standard solution,respectively. Auxiliary Information— Staff Liaison:Elena Gonikberg,Ph.D.,Scientist Expert Committee:(PA4)Pharmaceutical Analysis 4 USP28–NF23Page 1986 Phone Number:1-301-816-8251