Packaging and storage— Preserve in tight containers,in a cool place.

USP Reference standards á11ñ— USP Erythromycin RS.USP Erythromycin Estolate RS.

Identification— Transfer a quantity of Oral Suspension,equivalent to about 20mg of erythromycin,to a separator.Add 15mLof 0.02Nsodium hydroxide,and swirl to mix.Add 2g of sodium chloride and 25mLof chloroform,and shake for 3minutes.Drain the chloroform phase through a small amount of chloroform-washed anhydrous sodium sulfate,and collect the chloroform extract in a beaker,rinsing the sodium sulfate with an additional 10mLof chloroform.Evaporate the chloroform to dryness.Dissolve the residue in 1mLof methanol (test solution).Prepare a Standard solution by transferring a quantity of USP Erythromycin Estolate RS,equivalent to 20mg of erythromycin,to a separator and carrying out the extraction procedure described for preparation of the test solution.Apply separately 3µLof each solution to a thin-layer chromatographic plate (see Chromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel.Proceed as directed in the Identificationtest under Erythromycin Delayed-Release Capsules,beginning with “Place the plate in an unlined chromatographic chamber.”

Uniformity of dosage units á905ñ—

Deliverable volume á698ñ: meets the requirements.

pHá791ñ: between 3.5and 6.5.

Assay— Dilute an accurately measured volume of Oral Suspension,freshly mixed and free from air bubbles,quantitatively with methanol to obtain a solution containing the equivalent of 2.5mg of erythromycin per mL.Dilute with 1.5volumes of Buffer No.3,and allow to stand at room temperature for 18hours.Proceed as directed for erythromycin under Antibiotics—Microbial Assays á81ñ,using an accurately measured volume of this stock test solution diluted quantitatively with Buffer No.3to yield a Test Dilutionhaving a concentration assumed to be equal to the median dose level of the Standard.

Expert Committee:(PA7)Pharmaceutical Analysis 7

USP28–NF23Page 763

Phone Number:1-301-816-8335