Methyldopate Hydrochloride Injection
» Methyldopate Hydrochloride Injection is a sterile solution of Methyldopate Hydrochloride in Water for Injection. It contains not less than 90.0 percent and not more than 110.0 percent of the labeled amount of methyldopate hydrochloride (C12H17NO4·HCl).
Packaging and storage
Preserve in single-dose containers, preferably of Type I glass.
Identification
A:
Dilute a volume of Injection with a mixture of chloroform and methanol (1:1), if necessary, to obtain a solution containing about 5 mg of methyldopate hydrochloride per mL. Apply separately 10 µL of this solution and 10 µL of a Standard solution of USP Methyldopate Hydrochloride RS in a solvent mixture of chloroform and methanol (1:1) containing 5 mg per mL to a suitable thin-layer chromatographic plate (see Chromatography
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B:
It responds to the tests for Chloride
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Bacterial endotoxins
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pH
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Particulate matter
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Other requirements
It meets the requirements under Injections
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Assay
Buffer solution
To 214 g of monobasic potassium phosphate add 700 mL of water, and stir. Cautiously add 75 mL of sodium hydroxide solution (1 in 2), and stir until solution is complete. Adjust with sodium hydroxide solution (1 in 2) to a pH of 8.0, and dilute with water to 1000.0 mL.
Water-saturated tributyl phosphate
Shake 800 mL of tributyl phosphate with 100 mL of water, and discard the lower, aqueous phase. Filter the upper phase.
Standard preparation
Transfer about 25 mg of USP Methyldopate Hydrochloride RS, accurately weighed, to a 25-mL volumetric flask, add water to volume, and mix. Transfer 5 mL of this solution to a 100-mL volumetric flask, add 0.1 N sulfuric acid to volume, and mix. Use a freshly prepared solution. The Standard preparation contains about 50 µg per mL.
Assay preparation
Transfer to a 50-mL volumetric flask an accurately measured volume of Injection, equivalent to about 50 mg of methyldopate hydrochloride, add water to volume, and mix. Transfer a 5.0-mL aliquot of the solution to a 60-mL separator, add 15 mL of Buffer solution and 10 mL of Water-saturated tributyl phosphate, and shake for about 1 minute. Allow the phases to separate, and transfer the lower, aqueous phase to a second 60-mL separator. To this separator add a second 10-mL portion of Water-saturated tributyl phosphate, shake for about 1 minute, allow the phases to separate, discard the lower, aqueous phase, and add the upper tributyl phosphate phase to the phase retained in the first separator. Rinse the second separator with about 2 mL of Water-saturated tributyl phosphate, and add the rinsing to the first separator. Extract the phase contained in the first separator with two 25-mL portions of 0.1 N sulfuric acid. Collect the acid extracts in a 100-mL volumetric flask, add 0.1 N sulfuric acid to volume, and mix. Filter, if necessary, to obtain a clear solution.
Procedure
Concomitantly determine the absorbances of the Assay preparation and the Standard preparation in 1-cm cells at the wavelength of maximum absorbance at about 283 nm, with a suitable spectrophotometer, using 0.1 N sulfuric acid as the blank. Calculate the quantity, in mg, of methyldopate hydrochloride (C12H17NO4·HCl) in each mL of the Injection taken by the formula:
(C / V)(AU / AS)
in which C is the concentration, in µg per mL, of USP Methyldopate Hydrochloride RS in the Standard preparation; V is the volume, in mL, of Injection taken; and AU and AS are the absorbances of the Assay preparation and the Standard preparation, respectively.
Auxiliary Information
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USP32NF27 Page 2945
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