Packaging and storage— Preserve in tight containers.

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

Identification— Prepare a test solution by mixing a quantity of Erythromycin Estolate for Oral Suspension with methanol to obtain a concentration equivalent to about 20mg of erythromycin per mL.Prepare a Standard solution of USP Erythromycin Estolate RSin methanol containing the equivalent of 20mg of erythromycin per mL.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 5.0and 7.0(if pediatric drops,between 5.0and 5.5),in the suspension constituted as directed in the labeling.

Water,Method Iá921ñ: not more than 2.0%,20mLof methanol containing 10%of imidazole being used in place of methanol in the titration vessel.

Assay— Constitute Erythromycin Estolate for Oral Suspension as directed in the labeling,and proceed as directed in the Assayunder Erythromycin Estolate Oral Suspension.

Expert Committee:(PA7)Pharmaceutical Analysis 7

USP28–NF23Page 764

Phone Number:1-301-816-8335