Methyldopate Hydrochloride
;)
L-Tyrosine,3-hydroxy-a-methyl-,ethyl ester,hydrochloride.
L-3-(3,4-Dihydroxyphenyl)-2-methylalanine ethyl ester hydrochloride [5123-53-5;2508-79-4].
»Methyldopate Hydrochloride contains not less than 98.0percent and not more than 101.0percent of C12H17NO4·HCl,calculated on the dried basis.
Packaging and storage—
Preserve in well-closed containers.Store at 25
,excursions permitted between 15and 30.
,excursions permitted between 15and 30.
Identification—
B:Ultraviolet Absorption á197Uñ—
Solution:
50µg per mL.
Medium:
0.1Nhydrochloric acid.
Absorptivities at 280nm,calculated on the dried basis,do not differ by more than 3.0%.
D:
It responds to the tests for Chloride á191ñ,except that on the addition of the slight excess of 6Nammonium hydroxide a brown precipitate is formed.
Specific rotation á781Sñ:
between -13.5and -14.9(l=405nm).
and -14.9(l=405nm).
Test solution:
40mg per mL,in 0.1Nhydrochloric acid.
pHá791ñ:
between 3.0and 5.0,in a solution (1in 100).
Loss on drying á731ñ—
Dry it at 100and at a pressure not exceeding 5mm of mercury for 2hours:it loses not more than 0.5%of its weight.
and at a pressure not exceeding 5mm of mercury for 2hours:it loses not more than 0.5%of its weight.
Residue on ignition á281ñ:
not more than 0.1%.
Heavy metals,Method IIá231ñ:
0.001%.
Assay—
Mobile solvent—
Prepare a suitable solution of 0.02Mmonobasic sodium phosphate and 0.015Mphosphoric acid in a water and methanol solution (approximately 15.5:4.5)such that the retention time of methyldopate hydrochloride is approximately 6.5minutes.
Standard preparation—
Dissolve an accurately weighed quantity of USP Methyldopate Hydrochloride RSin the Mobile solventto obtain a solution containing about 1mg per mL.
Assay preparation—
Transfer about 50mg of Methyldopate Hydrochloride,accurately weighed,to a 50-mLvolumetric flask,dissolve in and dilute with Mobile solventto volume.
Procedure—
Introduce separately 20-µLportions of the Assay preparationand the Standard preparationinto a high-pressure liquid chromatograph (see Chromatography á621ñ)operated at 25,by means of a suitable microsyringe or sampling valve,adjusting the operating parameters such that the peak obtained with the Standard preparationis 100%full-scale.Typically,the apparatus is fitted with a 4-mm ×30-cm column that contains packing L1,is equipped with an UVdetector capable of monitoring absorption at 280nm and a suitable recorder,and is capable of operating at a column pressure between 700and 1700psi.In a suitable chromatogram,three replicate injections of the Standard preparationshow a relative standard deviation of not more than 1.5%.Determine the peak areas,at equivalent retention times,obtained with the Assay preparationand the Standard preparation,and calculate the quantity,in mg,of C12H17NO4·HCl in the portion of Methyldopate Hydrochloride taken by the formula:
,by means of a suitable microsyringe or sampling valve,adjusting the operating parameters such that the peak obtained with the Standard preparationis 100%full-scale.Typically,the apparatus is fitted with a 4-mm ×30-cm column that contains packing L1,is equipped with an UVdetector capable of monitoring absorption at 280nm and a suitable recorder,and is capable of operating at a column pressure between 700and 1700psi.In a suitable chromatogram,three replicate injections of the Standard preparationshow a relative standard deviation of not more than 1.5%.Determine the peak areas,at equivalent retention times,obtained with the Assay preparationand the Standard preparation,and calculate the quantity,in mg,of C12H17NO4·HCl in the portion of Methyldopate Hydrochloride taken by the formula:
50C(AU/AS),
in which Cis the concentration,in mg per mL,of USP Methyldopate Hydrochloride RSin the Standard preparation;and AUand ASare the peak areas 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 1262
Pharmacopeial Forum:Volume No.29(5)Page 1534
Phone Number:1-301-816-8305