FOR SOLID PACKAGED IN SINGLE-UNIT CONTAINERS: meets the requirements.

FOR SOLID PACKAGED IN SINGLE-UNIT CONTAINERS: between 9.0 and 11.0, in the suspension constituted as directed in the labeling.

FOR SOLID PACKAGED IN MULTIPLE-UNIT CONTAINERS: between 8.5 and 11.0, in the suspension constituted as directed in the labeling.

(Official January 1, 2007)

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

Solvent— Dissolve 2.2 g of monobasic potassium phosphate in 1590 mL of water, add 600 mL of isopropyl alcohol, 480 mL of alcohol, and 330 mL of acetonitrile, and mix. Adjust with 10 N potassium hydroxide to a pH of 8.4 ± 0.1, and shake by mechanical means for 30 minutes.

Assay preparation 1 (where packaged in a single-unit container)—Transfer the contents of a container of Azithromycin for Oral Suspension to a volumetric flask of such capacity, V, in mL, that when diluted to volume as directed in the following two sentences the solution will contain about 2 mg of azithromycin per mL. Add a volume of Solvent equal to about 70% of the volume of the flask, and shake by mechanical means for 30 minutes. Dilute with Solvent to volume, and mix. Transfer about 40 mL of this suspension to a stoppered centrifuge tube, and centrifuge for about 20 minutes. Transfer 2.0 mL of the clear supernatant to a 50-mL volumetric flask, dilute with Mobile phase to volume, and mix. Transfer 2.0 mL of this solution to a second 50-mL volumetric flask, dilute with Mobile phase to volume, and mix.

Assay preparation 2 (where packaged in a multiple-unit container)—Constitute Azithromycin for Oral Suspension as directed in the labeling. Transfer 5.0 mL of the suspension so obtained, freshly mixed and free from air bubbles, to a volumetric flask of such capacity, Vm, in mL, that when diluted to volume as directed below, the solution will contain about 0.4 mg of azithromycin per mL. Add a volume of Solvent equal to about 70% of the volume of the flask, and shake by mechanical means for 30 minutes. Dilute with Solvent to volume, and mix. Transfer about 40 mL of the suspension so obtained to a stoppered centrifuge tube, and centrifuge for about 20 minutes. Transfer 5.0 mL of the clear supernatant to a 50-mL volumetric flask, dilute with Mobile phase to volume, and mix. Transfer 5.0 mL of this solution to a second 50-mL volumetric flask, dilute with Mobile phase to volume, and mix.

Procedure— Proceed as directed for Procedure in the Assay under Azithromycin. Calculate the quantity, in mg, of azithromycin (C38H72N2O12) in the single-unit container of Azithromycin for Oral Suspension taken by the formula: in which rU is the azithromycin peak response obtained from Assay preparation 1; and the terms C, P, rU, and rS are as defined therein. Calculate the quantity, in mg, of azithromycin (C38H72N2O12) in each 5 mL of suspension taken from a container of Azithromycin for Oral Suspension where packaged in a multiple-unit container by the formula: in which rU is the azithromycin peak response obtained from Assay preparation 2; and the terms C, P, and rS are as defined therein.