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FOR POWDER PACKAGED IN SINGLE-UNIT CONTAINERS: meets the requirements.USP28

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FOR POWDER PACKAGED IN MULTIPLE-UNIT CONTAINERS:USP28 meets the requirements.

Mobile phase— Prepare a mixture of methanol and 0.067Mmonobasic potassium phosphate (600:400),adjust with phosphoric acid to a pHof 3.5,pass through a filter having a 0.5-µm or finer porosity,and degas.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Quantitatively dissolve an accurately weighed quantity of USP Clarithromycin RSin methanol,shaking and sonicating if necessary to effect dissolution,to obtain a solution having a known concentration of about 2100µg of clarithromycin (C38H69NO13)per mL,taking into account the stated potency,in µg per mg,of USP Clarithromycin RS.Transfer 10.0mLof this stock solution to a 50-mLvolumetric flask,dilute with Mobile phaseto 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 415µg of clarithromycin per mL.

Assay preparation— Constitute Clarithromycin for Oral Suspension as directed in the labeling.Transfer an accurately measured volume of the constituted Oral Suspension,equivalent to about 1to 2g of clarithromycin,with the aid of about 330mLof 0.067Mdibasic potassium phosphate,to a 1000-mLvolumetric flask containing about 50mLof 0.067Mdibasic potassium phosphate.Shake by mechanical means for 30minutes,dilute with methanol to volume,and mix.Sonicate for about 30minutes,and allow to cool.Dilute with methanol to volume,add a magnetic stirring bar,and stir for 60minutes.Allow to settle,and transfer an accurately measured volume of the clear supernatant,equivalent to about 20mg of clarithromycin,to a 50-mLvolumetric flask,dilute with Mobile phaseto 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 á621ñ)— 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 L1and is maintained at a constant temperature of about 50.The flow rate is about 1mLper 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 2100theoretical plates when calculated by the formula: the tailing factor is not less than 1.0and not more than 1.7;the capacity factor,k¢,is not less than 2.5and not more than 6;and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 50µL)of the Standard preparationand the Assay preparationinto the chromatograph,and measure the areas for the major peaks.Calculate the quantity,in mg,of C38H69NO13in each mLof the constituted Oral Suspension taken by the formula: in which Cis the concentration,in µg per mL,of clarithromycin (C38H69NO13)in the Standard preparation;Vis 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;and rUand rSare the clarithromycin peak area responses obtained from the Assay preparationand the Standard preparation,respectively.