Erythromycin and Benzoyl Peroxide Topical Gel, chemical structure, molecular formula, Reference Standards

Erythromycin and Benzoyl Peroxide Topical Gel

»Erythromycin and Benzoyl Peroxide Topical Gel is a mixture of Erythromycin in a suitable gel vehicle containing benzoyl peroxide and one or more suitable dispersants,stabilizers,and wetting agents.It contains not less than 90.0percent and not more than 125.0percent of the labeled amounts of erythromycin (C37H67NO13)and benzoyl peroxide (C14H10O4).

Packaging and storage— Before mixing,preserve the Erythromycin and the vehicle containing benzoyl peroxide in separate,tight containers.After mixing,preserve the mixture in tight containers.

USP Reference standards á11ñ— USP Erythromycin RS.

Identification— Prepare Standard preparationand an Assay preparationas directed in the Assay,except to omit the Internal standard solution,and chromatograph as directed in the Assay:the Assay preparationexhibits a major peak for benzoyl peroxide,the retention time of which corresponds to that exhibited by the Standard preparation.

Minimum fill á755ñ: meets the requirements.

Limit of benzoyl peroxide related substances—

Mobile phase A,Mobile phase B,Standard preparation A,Standard preparation B,Standard preparation C,Standard preparation D,Resolution solution,and Chromatographic system— Proceed as directed in the test for Related compoundsunder Benzoyl Peroxide Gel.

Test preparation— Transfer an accurately weighed quantity of Topical Gel,equivalent to about 100mg of benzoyl peroxide,to a 50-mLvolumetric flask,add 25mLof acetonitrile,shake vigorously to disperse the specimen,sonicate for 5minutes,dilute with acetonitrile to volume,mix,and filter.

Procedure— Proceed as directed for Procedurein the test for Related compoundsunder Benzoyl Peroxide Gel:it meets the limits stated.

Assay for erythromycin— Proceed as directed for erythromycin under Antibiotics—Microbial Assays á81ñ,using an accurately weighed portion of Topical Gel blended for 3to 5minutes in a high-speed glass blender jar containing 0.5mLof polysorbate 80and an accurately measured volume of Buffer No.3sufficient to obtain a stock solution having a convenient concentration of erythromycin.Dilute an accurately measured volume of this stock solution quantitatively with Buffer No.3to obtain a Test Dilutionhaving a concentration of erythromycin assumed to be equal to the median dose level of the Standard.

Assay for benzoyl peroxide—

Mobile phase,Internal standard solution,Standard preparation,and Chromatographic system— Proceed as directed in the Assayunder Benzoyl Peroxide Gel.

Assay preparation— Prepare as directed for Assay preparationin the Assayunder Benzoyl Peroxide Gel,using Topical Gel.

Procedure— Proceed as directed for Procedurein the Assayunder Benzoyl Peroxide Gel.Calculate the quantity,in mg,of benzoyl peroxide (C14H10O4)in the portion of Topical Gel taken by the formula:

125C(RU/RS),

in which Cis the concentration,in mg per mL,of benzoyl peroxide in the Standard preparation,and RUand RSare the ratios of benzoyl peroxide peak response to ethyl benzoate peak response obtained from the Assay preparationand the Standard preparation,respectively.

Auxiliary Information— Staff Liaison:William W.Wright,Ph.D.,Scientific Fellow

Expert Committee:(PA7)Pharmaceutical Analysis 7

USP28–NF23Page 762

Phone Number:1-301-816-8335