Prazosin Hydrochloride Capsules
»Prazosin Hydrochloride Capsules contain an amount of C19H21N5O4·HCl equivalent to not less than 90.0percent and not more than 110.0percent of the labeled amount of prazosin (C19H21N5O4).
Caution—Care should be taken to prevent inhaling particles of Prazosin Hydrochloride and to prevent its contacting any part of the body.
Packaging and storage— Preserve in well-closed,light-resistant containers.
Identification— To a portion of the contents of Capsules,equivalent to about 10mg of prazosin,add 20mLof a mixture of chloroform and methanol (1:1),shake by mechanical means for 10minutes,and centrifuge.Apply as separate 7.5-cm streaks 100µLof this solution and 100µLof a Standard solution of USP Prazosin Hydrochloride RSin a mixture of chloroform and methanol (1:1)containing about 0.5mg per mLto a suitable thin-layer chromatographic plate (seeChromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel mixture.Allow the streaks to dry,and develop the chromatogram in a solvent system consisting of a mixture of ethyl acetate and diethylamine (19:1)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 view under short-wavelength UVlight:prazosin appears as a dark blue band on a yellow-green fluorescent background,and theRFvalue of the prazosin band obtained from the solution from the Capsule contents corresponds to that obtained from the Standard solution.Spray the plate evenly with a 1in 50solution of hydrochloric acid in potassium iodoplatinate TS:the RFvalue of the principal band obtained from the solution from the Capsule contents corresponds to that obtained from the Standard solution.
Dissolution á711ñ—
Medium: 0.1Nhydrochloric acid containing 3%sodium lauryl sulfate;900mL.
Apparatus 1: 100rpm.
Time: 60minutes.
Procedure— Determine the amount of C19H21N5O4dissolved,employing the procedure set forth in theAssay,using a filtered portion of the solution under test as theAssay preparation in comparison with a Standard solution having a known concentration of USP Prazosin Hydrochloride RSin the sameMedium.
Tolerances— Not less than 75%(Q)of the labeled amount of C19H21N5O4is dissolved in 60minutes.
Uniformity of dosage units á905ñ: meet the requirements.
Procedure for content uniformity— Transfer the contents of a Capsule to a 100-mLvolumetric flask,add 50mLof 0.01Nmethanolic hydrochloric acid containing 30%water,shake by mechanical means for 15minutes,adjust with the same solvent to volume,and mix.Filter through a membrane filter having a porosity of 1.2µm and dilute,if necessary,a portion of the filtrate with the same solvent to a concentration of about 10µg of prazosin per mL.Prepare a Standard solution of USP Prazosin Hydrochloride RSin the same solvent having a known concentration of about 11µg per mL.Concomitantly determine the absorbances of the solution from the Capsule contents and the Standard solution in 1-cm cells at the wavelength of maximum absorbance at about 330nm,with a suitable spectrophotometer,using the solvent as the blank.Calculate the quantity,in mg,of prazosin (C19H21N5O4)in the Capsule taken by the formula:
(383.40/419.86)(0.001DC)(AU/AS),
in which 383.40and 419.86are the molecular weights of prazosin and prazosin hydrochloride,respectively;Dis the dilution factor for the Capsule contents;Cis the concentration,in µg per mL,of USP Prazosin Hydrochloride RS,calculated on the anhydrous basis,in the Standard solution;andAUandASare the absorbances of the solution from the Capsule contents and the Standard solution,respectively.
Assay—
Mobile phase,Chromatographic system,and Procedure— Proceed as directed in theAssayunder Prazosin Hydrochloride.
Acid–methanol solution— To 300mLof water in a 1000-mLvolumetric flask,add 0.85mLof hydrochloric acid,dilute with methanol to volume,and mix.Transfer 300mLof this solution to a 500-mLvolumetric flask,dilute with methanol to volume,and mix.
Standard preparation— Prepare a solution of USP Prazosin Hydrochloride RSinAcid–methanol solution having a known concentration of about 0.2mg per mL.Pipet 5mLof this solution into a 100-mLvolumetric flask,add 45.0mLofAcid–methanol solution,dilute with methanol to volume,and mix.
Assay preparation— Remove,as completely as possible,the contents of not less than 20Capsules,and weigh.Transfer a quantity of the contents,accurately weighed,equivalent to about 1mg of prazosin hydrochloride,to a glass-stoppered flask containing 50.0mLof Acid–methanol solution,and shake by mechanical means for 30minutes.Place the flask in an ultrasonic bath for 30minutes,cool to room temperature,and filter the contents through a membrane filter (5µm or finer porosity).Transfer 25.0mLof the filtrate to a 50-mLvolumetric flask,dilute with methanol to volume,and mix.
Procedure— Proceed as directed forProcedure in theAssay under Prazosin Hydrochloride.Calculate the quantity,in mg,of prazosin (C19H21N5O4)in the portion of the contents of Capsules taken by the formula:
(383.40/419.86)(0.1C)(rU/rS),
in which 383.40and 419.86are the molecular weights of prazosin and prazosin hydrochloride,respectively;Cis the concentration,in µg per mL,of USP Prazosin Hydrochloride RS,calculated on the anhydrous basis,in the Standard preparation;andrUandrSare the peak responses obtained from theAssay preparationand theStandard preparation,respectively.
Auxiliary Information— Staff Liaison:Andrzej Wilk,Ph.D.,Senior Scientific Associate
Expert Committee:(PA5)Pharmaceutical Analysis 5
USP28–NF23Page 1607
Pharmacopeial Forum:Volume No.28(2)Page 346
Phone Number:1-301-816-8305