Prepare a mixture of methanol and 0.067 M monobasic potassium phosphate (600:400), adjust with phosphoric acid to a pH of 3.5, pass through a filter having a 0.5-µm or finer porosity, and degas. Make adjustments if necessary (see System Suitability
under Chromatography 621
Quantitatively dissolve an accurately weighed quantity of USP Clarithromycin RS
in methanol, shaking and sonicating if necessary to effect dissolution, to obtain a solution having a known concentration of about 2100 µg of clarithromycin (C38
) per mL, taking into account the stated potency, in µg per mg, of USP Clarithromycin RS
. Transfer 10.0 mL of this stock solution to a 50-mL volumetric flask, dilute with Mobile phase
to volume, and mix. Pass a portion of this solution through a filter having a 0.5-µm or finer porosity, and use the filtrate as the Standard preparation.
This solution contains about 415 µg of clarithromycin per mL.
Constitute Clarithromycin for Oral Suspension as directed in the labeling. Transfer an accurately measured volume of the constituted Oral Suspension, equivalent to about 1 to 2 g of clarithromycin, with the aid of about 330 mL of 0.067 M dibasic potassium phosphate, to a 1000-mL volumetric flask containing about 50 mL of 0.067 M dibasic potassium phosphate. Shake by mechanical means for 30 minutes, dilute with methanol to volume, and mix. Sonicate for about 30 minutes, and allow to cool. Dilute with methanol to volume, add a magnetic stirring bar, and stir for 60 minutes. Allow to settle, and transfer an accurately measured volume of the clear supernatant, equivalent to about 20 mg of clarithromycin, to a 50-mL volumetric flask, dilute with Mobile phase to volume, mix, and pass through a filter having a 0.5-µm or finer porosity. Use the filtrate as the Assay preparation.
Chromatographic system (see Chromatography 621)
The liquid chromatograph is equipped with a 210-nm detector, an optional guard column that contains packing L1, and a 4.6-mm × 15-cm analytical column that contains packing L1 and is maintained at a constant temperature of about 50
. The flow rate is about 1 mL per minute. Chromatograph the Standard preparation,
and record the peak responses as directed for Procedure:
the column efficiency, determined from the clarithromycin peak, is not less than 2100 theoretical plates when calculated by the formula:
5.545(t/Wh / 2)2,
the tailing factor is not less than 1.0 and not more than 1.7; the capacity factor, k¢ ,
is not less than 2.5 and not more than 6; and the relative standard deviation for replicate injections is not more than 2.0%.
Separately inject equal volumes (about 50 µL) of the Standard preparation
and the Assay preparation
into the chromatograph, and measure the areas for the major peaks. Calculate the quantity, in mg, of C38
in each mL of the constituted Oral Suspension taken by the formula:
50(C/Vv)(rU / rS),
in which C
is the concentration, in µg per mL, of clarithromycin (C38
) in the Standard preparation; V
is the volume, in mL, of constituted Oral Suspension taken to prepare the Assay preparation; v
is the volume, in mL, of clear supernatant taken to prepare the Assay preparation;
are the clarithromycin peak area responses obtained from the Assay preparation
and the Standard preparation,