Erythromycin Stearate Tablets
» Erythromycin Stearate Tablets contain the equivalent of not less than 90.0 percent and not more than 120.0 percent of the labeled amount of erythromycin (C37H67NO13).
Packaging and storage Preserve in tight containers.
USP Reference standards 11
Identification To a quantity of powdered Tablets add a volume of methanol sufficient to yield a solution containing the equivalent of about 5 mg of erythromycin per mL. Shake this mixture by mechanical means for about 30 minutes. Centrifuge a portion of this mixture, and use the clear supernatant as the test solution. Prepare a Standard solution of USP Erythromycin Stearate RS in methanol containing about 8 mg per mL. Apply separately 20 µL each of the test solution and the Standard solution to a suitable thin-layer chromatographic plate (see Chromatography 621) coated with a 0.25-mm layer of chromatographic silica gel mixture, and allow to dry. Place the plate in an unlined chromatographic chamber, and develop the chromatograms in a solvent system consisting of a mixture of methanol and chloroform (85:15) until the solvent front has moved about 9 cm. Remove the plate from the chamber, mark the solvent front, and allow the solvent to evaporate. Spray the plate with a methanolic solution of 2¢,7¢-dichlorofluorescein (1 in 500), and examine the plate under long-wavelength UV light: the RF values of the principal fluorescent spots obtained from the test solution correspond to those obtained from the Standard solution. Then spray the plate with a mixture of dehydrated alcohol, p-methoxybenzaldehyde, and sulfuric acid (90:5:5). Heat the plate at 100 for 10 minutes, and examine the chromatograms, in which the erythromycin appears as a black-to-purple spot: the RF value of the principal spot obtained from the test solution corresponds to that obtained from the Standard solution.
Medium: 0.05 M pH 6.8 phosphate buffer (see under Solutions in the section Reagents, Indicators, and Solutions); 900 mL.
Apparatus 2: 100 rpm.
Time: 120 minutes.
Stock standard solution Dissolve an accurately weighed quantity of USP Erythromycin RS in methanol to obtain a solution containing about 14 mg per mL. Dilute quantitatively with water, and mix to obtain a solution having a known concentration of about 0.56 mg of USP Erythromycin RS per mL.
Working standard solution On the day of use, dilute 25.0 mL of Stock standard solution with water to 50.0 mL, and mix.
Test solution After 120 minutes, withdraw a portion of the solution under test, filter, and dilute with Medium, if necessary, to obtain a solution having an estimated concentration of about 0.28 mg of erythromycin per mL.
Procedure Transfer 5.0-mL portions of the Working standard solution to two 25-mL volumetric flasks, one of which serves as a working standard blank. Similarly, transfer 5.0-mL portions of the Test solution to two 25-mL volumetric flasks, one of which serves as a blank for that Test solution. To each of the flasks designated as a blank add 2.0 mL of 0.5 N sulfuric acid and to the remaining flasks add 2.0 mL of water. Allow to stand for 5 minutes with intermittent swirling. To all flasks add 15.0 mL of 0.25 N sodium hydroxide, dilute with Medium to volume, and mix. Heat the flasks in a water bath at 60 ± 0.5 for 5 minutes, and allow to cool. Using a suitable spectrophotometer, determine the absorbance of each solution, corrected for its blank solution, at the wavelength of maximum absorbance at about 236 nm. Determine the amount of C37H67NO13 dissolved from the Test solution in comparison with the solution obtained from the Working standard solution.
Tolerances Not less than 75% (Q) of the labeled amount of C37H67NO13 is dissolved in 120 minutes.
Uniformity of dosage units 905: meet the requirements.
Loss on drying 731 Dry about 100 mg of powdered Tablets in a capillary-stoppered bottle in vacuum at 60 for 3 hours: it loses not more than 5.0% of its weight.
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USP35NF30 Page 3094