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.
Identification—
Transfer a quantity of Intramammary Infusion, equivalent to about 5 mg of erythromycin, to a separator containing 50 mL of solvent hexane. Shake until dissolved. Extract with three separate 20-mL portions of methanol. Combine the methanol extracts in a beaker, and evaporate to dryness. Dissolve the residue in 2 mL of methanol (test solution). Proceed as directed in the
Identification test under
Erythromycin Delayed-Release Capsules, beginning with “Prepare a Standard solution of
USP Erythromycin RS.”
Water, Method I 
921
:
not more than 1.0%, 20 mL of 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 50 mL of solvent hexane. Shake until dissolved. Wash with four separate 20-mL portions of a mixture of methanol and water (4:1). Combine the washings in a 100-mL volumetric flask, dilute with the methanol and water solution to volume, and mix. Proceed as directed for erythromycin under
Antibiotics—Microbial Assays 81, using an accurately measured volume of this stock solution diluted quantitatively with
Buffer No. 3 to yield a
Test Dilution having a concentration of erythromycin assumed to be equal to the median dose level of the Reference Standard.
