U.S. PHARMACOPEIA

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Minoxidil Tablets
» Minoxidil Tablets contain not less than 90.0 percent and not more than 110.0 percent of the labeled amount of minoxidil (C9H15N5O).
Packaging and storage— Preserve in tight containers.
Identification— Transfer a portion of finely powdered Tablets, equivalent to about 10 mg of minoxidil, to a separator. Add 25 mL of water, and extract with three 15-mL portions of chloroform. Combine the chloroform extracts, and evaporate with the aid of a stream of nitrogen. Wash the inside of the container with about 5 mL of alcohol, add 300 mg of potassium bromide, and evaporate under vacuum at 50 until dry: the IR absorption spectrum of a potassium bromide dispersion prepared from the residue so obtained exhibits maxima at the same wavelengths as that of a similar preparation of USP Minoxidil RS.
Dissolution 711—
Medium: pH 7.2 phosphate buffer (see under Buffer Solutions in the section Reagents, Indicators, and Solutions); 900 mL.
Apparatus 1: 75 rpm.
Time: 15 minutes.
Procedure— Determine the amount of C9H15N5O dissolved from UV absorbances at the wavelength of maximum absorbance of filtered portions of the solution under test, suitably diluted with Dissolution Medium, if necessary, in comparison with a Standard solution having a known concentration of USP Minoxidil RS in the same medium. For Tablets containing up to 10 mg of minoxidil, measurement is made at about 231 nm; for Tablets containing more than 10 mg, the wavelength used is about 287 nm.
Tolerances— Not less than 75% (Q) of the labeled amount of C9H15N5O is dissolved in 15 minutes.
Uniformity of dosage units 905: meet the requirements.
Residual solvents 467: meet the requirements.
(Official January 1, 2007)
Assay—
Mobile phase , Internal standard solution, Standard preparation, and Chromatographic system—Proceed as directed in the Assay under Minoxidil.
Assay preparation— Weigh and finely powder not less than 10 Tablets. To an accurately weighed portion of the powder, equivalent to about 5 mg of minoxidil, add 20.0 mL of Internal standard solution, shake for 5 minutes, and centrifuge.
Procedure— Proceed as directed for Procedure in the Assay under Minoxidil. Calculate the quantity, in mg, of minoxidil (C9H15N5O) in the portion of Tablets taken by the formula:
20C(RU / RS),
in which the terms are as defined therein.
Auxiliary Information— Staff Liaison : Andrzej Wilk, Ph.D., Senior Scientific Associate
Expert Committee : (MDCV05) Monograph Development-Cardiovascular
USP29–NF24 Page 1442
Phone Number : 1-301-816-8305