Erythromycin Estolate Oral Suspension
» Erythromycin Estolate Oral Suspension contains the equivalent of not less than 90.0 percent and not more than 115.0 percent of the labeled amount of erythromycin (C37H67NO13). It contains one or more suitable buffers, colors, diluents, dispersants, and flavors.
Packaging and storage— Preserve in tight containers, in a cool place.
USP Reference standards 11
USP Erythromycin RS Click to View Structure
USP Erythromycin Estolate RS Click to View Structure
Identification— Transfer a quantity of Oral Suspension, equivalent to about 20 mg of erythromycin, to a separator. Add 15 mL of 0.02 N sodium hydroxide, and swirl to mix. Add 2 g of sodium chloride and 25 mL of chloroform, and shake for 3 minutes. 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 10 mL of chloroform. Evaporate the chloroform to dryness. Dissolve the residue in 1 mL of methanol (test solution). Prepare a Standard solution by transferring a quantity of USP Erythromycin Estolate RS, equivalent to 20 mg of erythromycin, to a separator and carrying out the extraction procedure described for preparation of the test solution. Apply separately 3 µL of each solution to a thin-layer chromatographic plate (see Chromatography 621) coated with a 0.25-mm layer of chromatographic silica gel. Proceed as directed in the Identification test under Erythromycin Delayed-Release Capsules, beginning with “Place the plate in an unlined chromatographic chamber.”
Uniformity of dosage units 905
For suspension packaged in single-unit containers: meets the requirements.
Deliverable volume 698: meets the requirements.
pH 791: between 3.5 and 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 2.5 mg of erythromycin per mL. Dilute with 1.5 volumes of Buffer No. 3, and allow to stand at room temperature for 18 hours. Proceed as directed for erythromycin under Antibiotics—Microbial Assays 81, using an accurately measured volume of this stock test solution diluted quantitatively with Buffer No. 3 to yield a Test Dilution having a concentration assumed to be equal to the median dose level of the Standard.
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