Labetalol Hydrochloride
;)
Benzamide,2-hydroxy-5-[1-hydroxy-2-[(1-methyl-3-phenylpropyl)amino]ethyl]-,monohydrochloride.
5-[1-Hydroxy-2-[(1-methyl-3-phenylpropyl)amino]ethyl]salicylamide monohydrochloride [32780-64-6].
»Labetalol Hydrochloride contains not less than 97.5percent and not more than 101.0percent of C19H24N2O3·HCl,calculated on the dried basis.
Packaging and storage—
Preserve in tight,light-resistant containers.Store at 25
,excursions permitted between 15and 30.
,excursions permitted between 15and 30.
pHá791ñ:
between 4.0and 5.0,in a solution (1in 100).
Loss on drying á731ñ:
Dry it in a vacuum at 105for 4hours:it loses not more than 1.0%of its weight.
for 4hours:it loses not more than 1.0%of its weight.
Residue on ignition á281ñ:
not more than 0.1%.
Heavy metals,Method IIá231ñ:
0.002%.
Chromatographic purity—
Detection reagent—
Transfer 2.5g of cadmium acetate to a 500-mLvolumetric flask,add 10mLof glacial acetic acid,dilute with alcohol to volume,and mix.Just prior to use,prepare a 0.2in 100solution of ninhydrin in the cadmium acetate solution for use as the Detection reagent.
Solvent mixture—
Prepare a solution of methanol and water (4:1),and mix.
Ammonium chloride reference solution—
Dissolve 60mg of ammonium chloride in 10.0mLof water,and mix.
Standard stock solution—
Dissolve USP Labetalol Hydrochloride RSin Solvent mixture,and mix to obtain a solution having a known concentration of 40mg per mL.
Standard solution 1—
Quantitatively dilute a portion of the Standard stock solutionwith Solvent mixtureto obtain a solution having a known concentration of 0.2mg per mL.
Standard solution 2—
Quantitatively dilute a portion of the Standard solution 1with Solvent mixtureto obtain a solution having a known concentration of 0.1mg per mL.
Test solution—
Dissolve 200mg of Labetalol Hydrochloride in 5.0mLof Solvent mixture,and mix.
Procedure I—Apply separately 5-µLportions of the Standard stock solution,Standard solution 1,Standard solution 2,and the Test solutionto a suitable thin-layer chromatographic plate (see Chromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel mixture.Allow the spots to dry,and develop the chromatograms in a solvent system consisting of a mixture of dichloromethane,methanol,and ammonium hydroxide (15:5:1)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,and allow the solvent to evaporate.Examine the plate under short-wavelength UVlight:the RFvalue of the principal spot from the Test solutioncorresponds to that of the principal spot from the Standard stock solution.
Spray the plate with Detection reagent,heat the plate at 105for 15minutes,cool to room temperature,and examine the chromatogram:no individual secondary spot observed in the chromatogram of the Test solutionis greater in size or intensity than the principal spot observed in the chromatogram of Standard solution 1(0.5%each).[NOTE—The spots appear as dark orange spots on a light orange to yellow background.A“negative image”spot (white)near the origin may be observed in the chromatogram of the Test solution.This is due to the formation of ammonium chloride during the chromatographic procedure and may be ignored.]
for 15minutes,cool to room temperature,and examine the chromatogram:no individual secondary spot observed in the chromatogram of the Test solutionis greater in size or intensity than the principal spot observed in the chromatogram of Standard solution 1(0.5%each).[NOTE—The spots appear as dark orange spots on a light orange to yellow background.A“negative image”spot (white)near the origin may be observed in the chromatogram of the Test solution.This is due to the formation of ammonium chloride during the chromatographic procedure and may be ignored.]
Procedure II—Apply separately 10-µLportions of the Ammonium chloride reference solution,the Standard stock solution,Standard solution 1,Standard solution 2,and the Test solutionto a suitable thin-layer chromatographic plate (see Chromatography á621ñ),coated with a 0.25-mm layer of chromatographic silica gel mixture.Allow the spots to dry,and develop the chromatograms in a solvent system consisting of a mixture of ethyl acetate,isopropyl alcohol,water,and ammonium hydroxide (25:15:8:2)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,and allow the solvent to evaporate.Examine the plate under short-wavelength UVlight:no individual secondary spot (other than that due to ammonium chloride)observed in the chromatogram of the Test solutionis greater in size or intensity than the principal spot observed in the chromatogram of Standard solution 1(0.5%each).
Total impurities—
The sum of the intensities of all secondary spots (other than those due to ammonium chloride)observed in the chromatograms of the Test solutionfrom both Procedure Iand Procedure IIdoes not exceed 1.0%.
Organic volatile impurities,Method Iá467ñ:
meets the requirements.
Diastereoisomer ratio—
1-Butaneboronic acid solution—
Dissolve 1-butaneboronic acid in pyridine,previously dried over a suitable molecular sieve,and mix to obtain a solution having a known concentration of 20mg per mL.
System suitability solution—
Dissolve an accurately weighed quantity of USP Labetalol Hydrochloride RSin 1-Butaneboronic acid solution,and dilute quantitatively and stepwise with 1-Butaneboronic acid solutionto obtain a solution having a known concentration of about 1.4mg of USP Labetalol Hydrochloride RSper mL.Allow the solution to stand at room temperature for 20minutes before using.
Test solution—
Transfer about 1mg of Labetalol Hydrochloride to a 1-mLreaction vial,add 0.7mLof 1-Butaneboronic acid solution,and mix until the labetalol hydrochloride is completely dissolved.Allow the solution to stand at room temperature for 20minutes before using.
Chromatographic system (see Chromatography á621ñ)—
The gas chromatograph is equipped with a flame-ionization detector and a 2-mm ×1.8-m glass column packed with 10%phase G3on 100-to 120-mesh support S1AB.The column temperature is maintained at about 320,and the injection port and the detector block temperatures are maintained at about 340.Nitrogen is used as the carrier gas at the flow rate of about 30mLper minute.Chromatograph the System suitability solution,and record the peak responses as directed for Procedure:the relative retention times are about 0.8for the diastereoisomer B1-butaneboronate derivative and 1.0for the diastereoisomer A1-butaneboronate derivative;the resolution,R,between the diastereoisomer A1-butaneboronate derivative and diastereoisomer B1-butaneboronate derivative peaks is not less than 1.5;and the relative standard deviation of the ratios of the peak areas of the diastereoisomers for replicate injections is not more than 2.0%.
,and the injection port and the detector block temperatures are maintained at about 340.Nitrogen is used as the carrier gas at the flow rate of about 30mLper minute.Chromatograph the System suitability solution,and record the peak responses as directed for Procedure:the relative retention times are about 0.8for the diastereoisomer B1-butaneboronate derivative and 1.0for the diastereoisomer A1-butaneboronate derivative;the resolution,R,between the diastereoisomer A1-butaneboronate derivative and diastereoisomer B1-butaneboronate derivative peaks is not less than 1.5;and the relative standard deviation of the ratios of the peak areas of the diastereoisomers for replicate injections is not more than 2.0%.
Procedure—
Inject about 2µLof the Test solutioninto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the diastereoisomer Acontent,in percentage,taken by the formula:
100rA/(rA+rB),
in which rAis the peak area of the diastereoisomer A1-butaneboronate derivative peak;and rBis the peak area of the diastereoisomer B1-butaneboronate derivative peak.The diastereoisomer Acontent is not less than 45.0%and not more than 55.0%.
Assay—
Mobile phase—
Prepare a suitable filtered and degassed mixture of 0.1Mmonobasic sodium phosphate and methanol (65:35).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).
Standard preparation—
Dissolve an accurately weighed quantity of USP Labetalol Hydrochloride RSin Mobile phaseto obtain a solution having a known concentration of about 0.4mg per mL.
Assay preparation—
Transfer about 40mg of Labetalol Hydrochloride,accurately weighed,to a 100-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.
Chromatographic system(see Chromatography á621ñ)—
The liquid chromatograph is equipped with a 230-nm detector and a 4.6-mm ×20-cm column that contains packing L1and is maintained at 60±1.The flow rate is about 1.5mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the column efficiency determined from the analyte peak is not less than 700theoretical 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 1.5%.
.The flow rate is about 1.5mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the column efficiency determined from the analyte peak is not less than 700theoretical 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 1.5%.
Procedure—
Separately inject equal volumes (about 5µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the area responses for the major peaks.Calculate the quantity,in mg,of labetalol hydrochloride (C19H24N2O3·HCl)in the portion of Labetalol Hydrochloride taken by the formula:
100C(rU/rS),
in which Cis the concentration,in mg per mL,of USP Labetalol Hydrochloride RSin the Standard preparation;and rUand rSare the peak area 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 1102
Pharmacopeial Forum:Volume No.29(6)Page 1916
Phone Number:1-301-816-8305