Packaging and storage— Preserve in single-dose disposable syringes that are well-closed containers.

Labeling— Label it to indicate that it is for veterinary use only.

USP Reference standards á11ñ— USP Erythromycin RS.

Identification— Transfer a quantity of Intramammary Infusion,equivalent to about 5mg of erythromycin,to a separator containing 50mLof solvent hexane.Shake until dissolved.Extract with three separate 20-mLportions of methanol.Combine the methanol extracts in a beaker,and evaporate to dryness.Dissolve the residue in 2mLof methanol (test solution).Proceed as directed in the Identificationtest under Erythromycin Delayed-Release Capsules,beginning with “Prepare a Standard solution of USP Erythromycin RS.”

Minimum fill á755ñ: meets the requirements.

Water,Method Iá921ñ: not more than 1.0%,20mLof a mixture of toluene and methanol (7:3)being used in place of methanol in the titration vessel.

Assay— Transfer the contents of a syringe of Intramammary Infusion to a separator containing 50mLof solvent hexane.Shake until dissolved.Wash with four separate 20-mLportions of a mixture of methanol and water (4:1).Combine the washings in a 100-mLvolumetric flask,dilute with the methanol and water solution to volume,and mix.Proceed as directed for erythromycin under Antibiotics—Microbial Assays á81ñ,using an accurately measured volume of this stock solution diluted quantitatively with Buffer No.3to yield a Test Dilutionhaving a concentration of erythromycin assumed to be equal to the median dose level of the Reference Standard.

Expert Committee:(VET)Veterinary Drugs

USP28–NF23Page 759

Phone Number:1-301-816-8178