Packaging and storage— Preserve in tight,light-resistant containers,and avoid exposure to excessive heat.

USP Reference standards á11ñ— USP Furazolidone RS.

Identification— Add a quantity of Oral Suspension,equivalent to about 50mg of furazolidone,to 10mLof a freshly prepared mixture of dimethylformamide and alcoholic potassium hydroxide TS(9:1):the solution turns purple,immediately changes to deep blue,and,upon standing for 10minutes,again turns purple.

pHá791ñ: between 6.0and 8.5.

Assay— Transfer an accurately measured volume of Oral Suspension,equivalent to about 160mg of furazolidone,to a suitable flask.Add 5mLof water,and mix.Transfer the mixture with the aid of dimethylformamide to a 1000-mLvolumetric flask.Add about 500mLof dimethylformamide,shake by mechanical means for 10minutes,dilute with dimethylformamide to volume,and mix.Transfer 5.0mLof this solution to a 100-mLvolumetric flask,dilute with water to volume,and mix (assay solution).Similarly,dissolve a suitable quantity of USP Furazolidone RS,accurately weighed,in dimethylformamide to obtain a Standard stock solution having a known concentration of about 160µg per mL.Transfer 5.0mLof this stock solution to a 100-mLvolumetric flask,dilute with water to volume,and mix (Standard solution).Concomitantly determine the absorbances of the assay solution and the Standard solution at the wavelength of maximum absorbance at about 367nm,with a suitable spectrophotometer,using dimethylformamide solution (1in 20)as the blank.Calculate the quantity,in mg,of furazolidone (C8H7N3O5)in each mLof the Oral Suspension taken by the formula: in which Cis the concentration,in µg per mL,of USP Furazolidone RSin the Standard solution;Vis the volume,in mL,of Oral Suspension taken;and AUand ASare the absorbances of the assay solution and the Standard solution,respectively.

Expert Committee:(VET)Veterinary Drugs

USP28–NF23Page 875

Phone Number:1-301-816-8178