Neomycin Sulfate,Isoflupredone Acetate,and Tetracaine Hydrochloride Ointment, chemical structure, molecular formula, Reference Standards

Neomycin Sulfate,Isoflupredone Acetate,and Tetracaine Hydrochloride Ointment

»Neomycin Sulfate,Isoflupredone Acetate,and Tetracaine Hydrochloride Ointment contains the equivalent of not less than 90.0percent and not more than 120.0percent of the labeled amount of neomycin,and not less than 92.5percent and not more than 117.5percent of the labeled amounts of isoflupredone acetate (C23H29FO6)and tetracaine hydrochloride (C15H24N2O2·HCl)in a suitable ointment base.

Packaging and storage— Preserve in collapsible tubes or well-closed containers.

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

USP Reference standards á11ñ— USP Isoflupredone Acetate RS.USP Neomycin Sulfate RS.USP Tetracaine Hydrochloride RS.

Identification—

A: Thin-Layer Chromatographic Identification Test á201ñ—

Test solution— To 2g of Ointment in a centrifuge tube add 25mLof chloroform,and heat at 60

for 5minutes,with occasional shaking.Centrifuge,discard the chloroform layer,add 5mLof water,shake,and filter.Use the filtrate.

Standard solution— Prepare a solution containing 2mg of USP Neomycin Sulfate RSper mL.

Application volume: 1µL.

Developing solvent system: a mixture of water,butyl alcohol,glacial acetic acid,and pyridine (35:30:22:6).

Spray reagent: a solution of triketohydrindene hydrate in butyl alcohol (2in 1000).

Procedure— Proceed as directed in the chapter,except to locate the spots by spraying with Spray reagentand heating at 100

for 5minutes.

B: The retention time of the major peak for isoflupredone acetate in the chromatogram of the Assay preparationcorresponds to that in the chromatogram of the Standard preparation,as obtained in the Assay for isoflupredone acetate.

Minimum fill á755ñ: meets the requirements.

Water,Method Iá921ñ: not more than 1.0%,a mixture of methanol and chloroform (3:2)being used instead of methanol in the titration vessel and the titration vessel being heated to between 45

and 55

Assay for neomycin— Proceed as directed under Antibiotics—Microbial Assays á81ñ.Place an accurately weighed portion of Ointment in a centrifuge tube with 25mLof chloroform.Heat at 60

for 3minutes,shake until the Ointment is dissolved,centrifuge,and remove and discard the chloroform.Add 15mLof chloroform,shake,centrifuge,and remove and discard the chloroform.Add 5.0mLof water and 15mLof chromatographic n-heptane,shake,centrifuge,and remove and discard the n-heptane layer.Dilute an accurately measured volume of the water layer quantitatively with Buffer No.3to obtain a Test Dilutionhaving a concentration of neomycin assumed to be equal to the median dose level of the Standard.

Assay for isoflupredone acetate—

Mobile phase,Diluent,Internal standard solution,Standard preparation,and Chromatographic system— Proceed as directed in the Assayunder Isoflupredone Acetate.

Assay preparation— Transfer an accurately weighed portion of Ointment,equivalent to about 4mg of isoflupredone acetate,to a suitable container.Add 8.0mLof Internal standard solution,32.0mLof Diluent,and about 10glass beads.Shake for about 15minutes,centrifuge,and use the clear chloroform portion.

Procedure— Proceed as directed in the Assayunder Isoflupredone Acetate.Calculate the quantity,in mg,of isoflupredone acetate (C23H29FO6)in the portion of Ointment taken by the formula:

WS(RU/RS),

in which the terms are as defined therein.

Assay for tetracaine hydrochloride—

Standard preparation— Prepare a solution in chloroform having a known concentration of about 5.0µg of USP Tetracaine Hydrochloride RSper mL.

Assay preparation— Transfer an accurately weighed portion of Ointment,equivalent to about 1.25mg of tetracaine hydrochloride,to a 250-mLvolumetric flask,add about 100mLof chloroform,and warm on a steam bath for about 3minutes to dissolve the Ointment.Cool to room temperature,dilute with chloroform to volume,and mix.

Blank solution— Transfer an accurately weighed portion of the ointment base,equivalent to the weight used in the Assay preparation,to a 250-mLvolumetric flask.Add 100mLof chloroform,warm on a steam bath for about 3minutes to dissolve,and allow to stand until the solution has equilibrated to room temperature.Dilute with chloroform to volume,and mix well.

Procedure— Concomitantly determine the absorbances of the Standard preparation,the Blank solution,and the Assay preparationwith a suitable spectrophotometer at the wavelength of maximum absorbance at about 310nm,using chloroform to zero the instrument.Calculate the absorbance of the Blank solution,AB,adjusted for weight difference between the Assay preparationand the Blank solution,by the formula:

A(WT/WB),

in which Ais the absorbance of the Blank solution;WTis the weight,in mg,of Ointment taken to prepare the Assay preparation;and WBis the weight,in mg,of the ointment base taken to prepare the Blank solution.Calculate the quantity,in mg,of tetracaine hydrochloride (C15H24N2O2·HCl)in the portion of Ointment taken by the formula:

250C[(AU-AB)/AS],

in which Cis the concentration,in mg per mL,of USP Tetracaine Hydrochloride RSin the Standard preparation;ABis as obtained above;and AUand ASare the absorbances of the Assay preparationand the Standard preparation,respectively.

Auxiliary Information— Staff Liaison:Ian DeVeau,Ph.D.,Senior Scientist

Expert Committee:(VET)Veterinary Drugs

USP28–NF23Page 1350

Pharmacopeial Forum:Volume No.27(4)Page 2758

Phone Number:1-301-816-8178