Identification—
The solution prepared for measurement of absorbance in the
Assay exhibits maxima and minima at the same wavelengths as the
Standard preparation prepared as directed in the
Assay.
Assay—
Standard preparation—
Transfer about 45 mg of
USP Oxymorphone RS, accurately weighed, to a 50-mL volumetric flask, dissolve in about 10 mL of chloroform, dilute with chloroform to volume, and mix. Transfer 15.0 mL of this solution to a 100-mL volumetric flask, dilute with chloroform to volume, and mix. The concentration of
USP Oxymorphone RS in the
Standard preparation is about 135 µg per mL.
Assay preparation—
Transfer an accurately measured volume of Injection, equivalent to about 15 mg of oxymorphone hydrochloride, to a 125-mL separator, and add water, if necessary, to bring the volume to 15 mL. Adjust by the addition of hydrochloric acid to a pH of less than 2, extract with five 15-mL portions of chloroform, and discard the chloroform extracts. Adjust the aqueous phase with ammonium hydroxide to a pH of 9.5, and extract with four 20-mL portions of chloroform. Filter the chloroform extracts through a chloroform-moistened pledget of cotton into a 100-mL volumetric flask, dilute with chloroform to volume, and mix.
Procedure—
Concomitantly determine the absorbances of the solutions in 1-cm cells at the wavelength of maximum absorbance at about 282 nm, with a suitable spectrophotometer, using chloroform as the blank. Calculate the quantity, in mg, of C
17H
19NO
4·HCl in each mL of the Injection taken by the formula:
(337.80 / 301.34)(0.1C / V)(AU / AS),
in which 337.80 and 301.34 are the molecular weights of oxymorphone hydrochloride and oxymorphone, respectively;
C is the concentration, in µg per mL, of
USP Oxymorphone 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.
85
—
It contains not more than 238.1 USP Endotoxin Units per mg of oxymorphone hydrochloride.