Enalapril Maleate and Hydrochlorothiazide Tablets
»Enalapril Maleate and Hydrochlorothiazide Tablets contain not less than 90.0percent and not more than 110.0percent of the labeled amounts of Enalapril Maleate (C20H28N2O5·C4H4O4)and Hydrochlorothiazide (C7H8ClN3O4S2).
Packaging and storage— Preserve in well-closed containers.
Identification—
A: The retention time of the major peak in the chromatogram of the Assay preparationcorresponds to that of the Standard preparationobtained as directed in the Assay for enalapril maleate.
B: The retention time of the major peak in the chromatogram of the Assay preparationcorresponds to that of the Standard preparationobtained as directed in the Assay for hydrochlorothiazide.
Dissolution á711ñ
Medium: water;900mL.
Apparatus 2: 50rpm.
Time: 30minutes.
Determine the amount of C20H28N2O5·C4H4O4dissolved,using filtered portions of the solution under test and following the Procedure for content uniformity of enalapril maleate,making any necessary volumetric adjustments,in comparison with a Standard solution of USP Enalapril Maleate RShaving similar concentrations in the same medium.
Determine the amount of C7H8ClN3O4S2dissolved by employing UVabsorption at the wavelength of maximum absorbance at about 320nm and at 360nm in 1-cm cells,on filtered portions of the solution under test,suitably diluted with Dissolution Medium,in comparison with a Standard solution having a known concentration of USP Hydrochlorothiazide RSdissolved in 20mLof methanol and diluted with Dissolution Medium.
Tolerances— Not less than 80%(Q)of the labeled amount of enalapril maleate (C20H28N2O5·C4H4O4)and not less than 60%(Q)of the labeled amount of hydrochlorothiazide (C7H8ClN3O4S2)are dissolved in 30minutes.
Uniformity of dosage units á905ñ: meet the requirements.
Procedure for content uniformity of enalapril maleate—
Buffer solution A Dissolve 136g of monobasic potassium phosphate in 800mLof water,adjust with phosphoric acid to a pHof 4.0,dilute with water to 1000mL,and mix.
Buffer solution B Transfer 20.0mLof Buffer solution Ato a 1000-mLvolumetric flask,dilute with water to volume,and mix.
Mobile phase Prepare a filtered and degassed mixture of water,acetonitrile,and Buffer solution A(34:15:1).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).
Standard preparation Dissolve an accurately weighed quantity of USP Enalapril Maleate RSin Buffer solution Bto obtain a solution having a known concentration of about 100µg per mL.
Test preparation Transfer one finely powdered Tablet to a 50-mLvolumetric flask,add about 30mLof Buffer solution B,and sonicate for 15minutes.Shake on a mechanical shaker for 30minutes,dilute with Buffer solution Bto volume,sonicate for 30minutes,mix,and filter,discarding the first portion of the filtrate.Dilute a portion of the filtrate with Buffer solution Bquantitatively to obtain a solution containing about 100µg per mL.
Chromatographic system(see Chromatography á621ñ) The liquid chromatograph is equipped with a 215-nm detector and a 4.6-mm ×20-cm column containing 10-µm packing L7and maintained at a temperature of 80.The flow rate is about 2mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the capacity factor,k¢,is not less than 2.5,the column efficiency determined from the analyte peak is not less than 1000theoretical plates,the tailing factor for the analyte peak is not more than 2.0,and the relative standard deviation for replicate injections is not more than 2.0%.
Procedure Separately inject equal volumes (about 50µL)of the Test preparationand the Standard preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of C20H28N2O5·C4H4O4in the Tablet taken by the formula:
(TC/D)(rU/rS),
in which Tis the labeled quantity,in mg,of enalapril maleate in the Tablet,Cis the concentration,in µg per mL,of USP Enalapril Maleate RSin the Standard preparation,Dis the concentration,in µg per mL,of enalapril maleate in the Test preparation,based upon the labeled quantity per Tablet and the extent of dilution,and rUand rSare the enalapril peak responses obtained from the Test preparationand the Standard preparation,respectively.
Procedure for content uniformity of hydrochlorothiazide—
Buffer solutionAand Buffer solutionB Prepare as directed under Procedure for content uniformity of enalapril maleate.
Standard preparation Transfer about 50mg of USP Hydrochlorothiazide RS,accurately weighed,to a 200-mLvolumetric flask.Add 20mLof methanol to dissolve the material,dilute with Buffer solution Bto volume,and mix to obtain a stock solution.Transfer 5.0mLof the stock solution to a 25-mLvolumetric flask,dilute with Buffer solution Bto volume,and mix to obtain a solution having a known concentration of about 50µg per mL.
Test preparation Transfer one Tablet to a volumetric flask of a suitable size such that,when the hydrochlorothiazide is dissolved from the Tablet,a solution having a concentration of about 250µg per mLis obtained.Add a volume of Buffer solution Bequal to about half the capacity of the flask,and sonicate with occasional shaking for 15minutes.Shake on a mechanical shaker for 30minutes,dilute with Buffer solution Bto volume,sonicate for 30minutes,mix,and filter,discarding the first portion of the filtrate.Transfer 5.0mLof the clear filtrate to a 25-mLvolumetric flask,dilute with Buffer solution Bto volume,and mix.
Procedure Determine the absorbances of the Standard preparationand the Test preparationin 1-cm cells at the wavelength of maximum absorbance at about 320nm and at 360nm,with a suitable spectrophotometer,relative to Buffer solution Bas the blank.Calculate the quantity,in mg,of C7H8ClN3O4S2in the Tablet taken by the formula:
(TC/D)(A320A360)U/(A320A360)S,
in which Tis the labeled quantity,in mg,of hydrochlorothiazide in the Tablet;Cis the concentration,in µg per mL,of USP Hydrochlorothiazide RSin the Standard preparation;Dis the concentration,in µg per mL,of hydrochlorothiazide in the Test preparation,based upon the labeled quantity per Tablet and the extent of dilution;and the parenthetic expressions are the differences in absorbances of the two solutions at the wavelengths indicated by the subscripts for the Test preparation(U)and the Standard preparation(S),respectively.
Related compounds—
Buffer solution and Mobile phase— Proceed as directed in the Assay for enalapril maleate.
Test solution— Use the Assay preparationprepared as directed in the Assay for enalapril maleate.
Enalaprilat solution— Transfer about 10mg of USP Enalaprilat RS,accurately weighed,to a 25-mLvolumetric flask,dilute with water to volume,and mix.
Enalapril diketopiperazine solution— Carefully place about 20mg of USP Enalapril Maleate RSin a 100-mLbeaker to form a mound on the bottom of the beaker.Place the beaker on a hot plate at about one-half the maximum hot plate temperature setting.Heat for about 5to 10minutes until the solid is melted.Immediately remove the beaker from the hot plate,and allow to cool.[NOTE—Avoid overheating to prevent heat-induced degradation,which would give rise to a brown color.]To the cooled residue in the beaker add 50mLof acetonitrile,and sonicate for a few minutes to dissolve.The solution typically contains,in each mL,between 0.2mg and 0.4mg of enalapril diketopiperazine.
Standard solution— Transfer about 40mg of USP Enalapril Maleate RS,accurately weighed,to a 200-mLvolumetric flask,and dissolve with about 50mLof methanol.Pipet 1mLeach of Enalaprilat solutionand Enalapril diketopiperazine solutioninto the volumetric flask,dilute with Buffer solutionto volume,and mix.
Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 215-nm detector and a 4.6-mm ×25-cm column that contains 5-µm packing L7.The column temperature is maintained at 65,and the flow rate is about 1.5mLper minute.Chromatograph the Standard solution,and record the peak responses as directed for Procedure:the relative retention times are about 0.3,0.4,and 1.0for enalaprilat,enalapril diketopiperazine,and enalapril,respectively;the resolution,R,between any of the peaks is not less than 1.3;the column efficiency is not less than 700theoretical plates for enalapril,1500for enalaprilat,and 1500for enalapril diketopiperazine;the tailing factor is not more than 3.5;and the relative standard deviation for replicate injections is not more than 5.0%for enalaprilat and enalapril diketopiperazine and not more than 2.0%for enalapril.
Procedure— Separately inject equal volumes (about 50µL)of the Standard solutionand the Test solutioninto the chromatograph,record the chromatograms,and measure the responses for the peaks.Calculate the quantity,in mg,of enalaprilat (enalapril related compound A)in the portion of Tablets taken by the formula:
0.2C(rU/rS),
in which Cis the concentration,in µg per mL,of enalaprilat in the Standard solution;and rUand rSare the peak responses of enalaprilat obtained from the Test solutionand the Standard solution,respectively.
Calculate the quantity,in mg,of enalapril diketopiperazine in the portion of Tablets taken by the formula:
0.2C(rU/rS),
in which Cis the concentration,in µg per mL,of enalapril diketopiperazine in the Standard solution;and rUand rSare the peak responses of enalapril diketopiperazine obtained from the Test solutionand the Standard solution,respectively:not more than 5.0%of total related compounds is found,calculated on the basis of the portion of Tablets taken as directed under Assay for enalapril maleate.
Assay for enalapril maleate—
Buffer solution— Transfer 136mg of monobasic potassium phosphate to a 1000-mLvolumetric flask,add 800mLof water,adjust with phosphoric acid to a pHof 2.0,dilute with water to volume,and mix.
Mobile phase— Prepare a degassed and filtered solution of Buffer solutionand acetonitrile (6:4).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).
Standard preparation— Transfer about 40mg of USP Enalapril Maleate RS,accurately weighed,to a 200-mLvolumetric flask,add about 50mLof methanol to dissolve,dilute with Buffer solutionto volume,and mix.
Assay preparation— Weigh and finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 40mg of enalapril maleate,to a 200-mLvolumetric flask,add about 50mLof Buffer solution,and sonicate for 15minutes.Add about 50mLof methanol to the flask,sonicate for 15minutes,dilute with Buffer solutionto volume,mix,and filter.
Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 215-nm detector and a 4.6-mm ×25-cm column that contains 5-µm packing L7.The column temperature is maintained at 65,and the flow rate is about 1.5mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the column efficiency is not less than 700theoretical plates;the tailing factor is not more than 3.5;and the relative standard deviation for replicate injections is not more than 2.0%.
Procedure— Separately inject equal volumes (about 50µL)of the Assay preparationand the Standard preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of enalapril maleate (C20H28N2O5·C4H4O4)in the portion of Tablets taken by the formula:
200C(rU/rS),
in which Cis the concentration,in µg per mL,of USP Enalapril Maleate RSin the Standard preparation;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.
Assay for hydrochlorothiazide—
Buffer solution— Prepare as directed under Assay for enalapril maleate.
Mobile phase— Prepare a filtered and degassed mixture of Buffer solutionand acetonitrile (9:1).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).
Standard preparation— Transfer about 20mg of USP Hydrochlorothiazide RS,accurately weighed,to a 200-mLvolumetric flask,add about 50mLof methanol to dissolve,dilute with Buffer solutionto volume,and mix.
Assay preparation— Prepare as directed for the Assay preparationunder Assay for enalapril maleate,except to weigh a portion of the powdered Tablets equivalent to about 20mg of hydrochlorothiazide.
Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 310-nm detector and a 4.6-mm ×20-cm column that contains 10-µm packing L7.The column temperature is maintained at 30,and the flow rate is about 2.5mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the capacity factor,k¢,is not less than 2.0,the column efficiency is not less than 1000theoretical plates,the tailing factor is not more than 2.0,and the relative standard deviation for replicate injections is not more than 2.0%.
Procedure— Separately inject equal volumes (about 50µL)of the Assay preparationand the Standard preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of hydrochlorothiazide (C7H8ClN3O4S2)in the portion of Tablets taken by the formula:
200C(rU/rS),
in which Cis the concentration,in µg per mL,of USP Hydrochlorothiazide RSin the Standard preparation;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.
Auxiliary Information— Staff Liaison:Andrzej Wilk,Ph.D.,Senior Scientific Associate
Expert Committee:(PA5)Pharmaceutical Analysis 5
USP28–NF23Page 732
Pharmacopeial Forum:Volume No.27(3)Page 2541
Phone Number:1-301-816-8305