Packaging and storage— Preserve in disposable syringes that are well-closed containers,except that where the Intramammary Infusion is labeled as sterile,the individual syringes or cartons are sealed and tamper-proof so that sterility is assured at time of use.

USP Reference standards á11ñ— USP Cloxacillin Sodium RS.

Labeling— Label it to indicate that it is for veterinary use only.Intramammary Infusion that is sterile may be so labeled.

Identification,Infrared Absorption á197Kñ— Obtain the test specimen as follows.Transfer a quantity of Intramammary Infusion,equivalent to about 500mg of cloxacillin,to a 50-mLcentrifuge tube,add 15mLof isooctane,mix,and centrifuge.Decant and discard the isooctane.Wash the residue with two 15-mLportions of isooctane and two 15-mLportions of ethyl ether,and discard the washings.Dry the residue in a current of air.

Sterility á71ñ(where labeled as being sterile)— It meets the requirements when tested as directed for Direct Inoculation of the Culture Medium under Test for Sterility of the Product to be Examined,except to use Fluid Thioglycollate Medium containing polysorbate 80solution (1in 200)and an amount of sterile penicillinase sufficient to inactivate the cloxacillin in each tube,to use Soybean–Casein Digest Medium containing polysorbate 80solution (1in 200)and an amount of sterile penicillinase sufficient to inactivate the cloxacillin in each tube,and to shake the tubes once daily.

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— Proceed as directed for cloxacillin 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 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 526

Phone Number:1-301-816-8178