Packaging and storage— Preserve in well-closed disposable syringes.

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

USP Reference standards á11ñ— USP Penicillin G Potassium RS.USP Penicillin G Procaine RS.

Identification— Transfer a portion of it,equivalent to about 100,000Penicillin G Units,to a test tube,add 25mLof methanol,and shake.Allow to separate,and use the methanol layer as the test solution.Prepare a Standard solution of USP Penicillin G Procaine RSin methanol containing about 4.5mg per mL.Apply separately 10µLof each solution to a thin-layer chromatographic plate (see Chromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel mixture.Allow the spots to dry,and develop the chromatogram in a solvent system consisting of a mixture of butanol,isopropyl alcohol,acetone,and water (4:4:2:2)until the solvent front has moved about three-fourths of the length of the plate.Remove the plate from the developing chamber,mark the solvent front,and allow the solvent to evaporate.Expose the plate to iodine vapors in a closed chamber for about 15minutes,and locate the spots:the RFvalues and colors of the two principal spots obtained from the test solution correspond to those obtained from the Standard solution.

Water,Method Iá921ñ: not more than 1.4%,20mLof a mixture of toluene and methanol (7:3)being used in place of methanol in the titration vessel.

Assay— Proceed as directed under Antibiotics—Microbial Assays á81ñ,expelling the contents of 1syringe of Intramammary Infusion into a high-speed glass blender jar containing 499.0mLof Buffer No.1and 1.0mLof polysorbate 80,and blending for 3to 5minutes.Allow to stand for about 10minutes,and dilute an accurately measured volume of the aqueous phase quantitatively and stepwise with Buffer No.1to obtain a Test Dilutionhaving a concentration assumed to be equal to the median dose level of the Standard.

Expert Committee:(VET)Veterinary Drugs

USP28–NF23Page 1490

Phone Number:1-301-816-8178