Mobile phase, Diluent, Resolution solution, Standard preparation, and Chromatographic system— Proceed as directed in the Assay under Doxycycline Hyclate.

Assay preparation 1 (where it is represented as being in a single-dose container)—Constitute Doxycycline for Injection as directed in the labeling. Withdraw all of the withdrawable contents, using a suitable hypodermic needle and syringe, and dilute quantitatively with Diluent to obtain a solution containing the equivalent of about 1000 µg of doxycycline per mL.

Assay preparation 2 (where the label states the quantity of doxycycline equivalent in a given volume of constituted solution)—Constitute Doxycycline for Injection as directed in the labeling. Dilute an accurately measured volume of the constituted solution quantitatively with Diluent to obtain a solution containing the equivalent of about 1000 µg of doxycycline per mL.

Procedure— Proceed as directed for Procedure in the Assay under Doxycycline Hyclate. Calculate the quantity, in mg, of doxycycline (C22H24N2O8) withdrawn from the container, or in the portion of constituted solution taken by the formula: in which L is the labeled quantity, in mg, of doxycycline in the container, or in the volume of constituted solution taken, D is the concentration, in µg of doxycycline per mL, of Assay preparation 1 or Assay preparation 2, based on the labeled quantity in the container or in the portion of constituted solution taken, respectively, and the extent of dilution, and the other terms are as defined therein.