Packaging and storage—
Preserve in tight containers, in a cool place.
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.”
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.
Auxiliary Information—
Staff Liaison :
Brian D. Gilbert, Ph.D., Scientist
Expert Committee : (MDANT05) Monograph Development-Antibiotics
USP29–NF24 Page 835
Pharmacopeial Forum : Volume No. 27(4) Page 2731
Phone Number : 1-301-816-8223
