Identification—
To an accurately measured volume of Oral Suspension, equivalent to about 50 mg of doxycycline, add 50 mL of methanol, shake, and allow to settle. Using the clear supernatant as the
Test Solution, proceed as directed for
Method II under
Identification—Tetracyclines 
193
.
Assay—
Mobile phase, Resolution solution, Standard preparation, and Chromatographic system—
Proceed as directed in the
Assay under
Doxycycline Hyclate.
Edetate diluent—
Transfer 5.2 g of edetate disodium to a 500-mL volumetric flask, add about 400 mL of
Mobile phase, sonicate for about 10 minutes or until dissolved, dilute with
Mobile phase to volume, and mix.
Assay preparation—
Constitute Oral Suspension as directed in the labeling. Transfer an accurately measured portion of the constituted oral suspension, freshly mixed and free from air bubbles, equivalent to about 100 mg of doxycycline, to a 100-mL volumetric flask, add 50 mL of Edetate diluent, sonicate for 15 minutes, and then shake by mechanical means for about 15 minutes. Dilute with Edetate diluent to volume, and mix. Pass through filter paper, discarding the first 10 mL of the filtrate, then pass through a filter having a 0.5-µm or finer porosity.
Procedure—
Proceed as directed for
Procedure in the
Assay under
Doxycycline Hyclate. Calculate the quantity, in mg, of doxycycline (C
22H
24N
2O
8) in each mL of the Oral Suspension taken by the formula:
0.1(CP / V)(rU / rS),
in which
V is the volume, in mL, of Oral Suspension taken to prepare the
Assay preparation; and the other terms are as defined therein.
