Packaging and storage— Preserve in tight containers,protected from light,and avoid prolonged exposure to temperatures exceeding 30.

Identification— Place an amount of Cream,equivalent to about 50mg of benzocaine,in a small beaker,add 20mLof 0.5Nhydrochloric acid,warm gently to disperse the cream,cool,and filter.To 10mLof the filtrate add 5drops of a solution of sodium nitrite (1in 10)and 2drops of methyl red TS,and neutralize with 1Nsodium hydroxide.Add 2mLof a solution of 100mg of 2-naphthol in 5mLof 1Nsodium hydroxide:an orange-red precipitate is formed.

Microbial limits á61ñ— It meets the requirements of the tests for absence of Staphylococcus aureusand Pseudomonas aeruginosa.

Minimum fill á755ñ: meets the requirements.

Assay— Weigh accurately an amount of Cream,equivalent to about 200mg of benzocaine,in a tared 250-mLbeaker.Add 50mLof water and 5mLof hydrochloric acid,and stir by mechanical means,with gentle warming,until solution is effected.Cool the solution in an ice bath to about 10,and titrate slowly with 0.1Msodium nitrite VS,determining the endpoint potentiometrically using a calomel-platinum electrode system.Each mLof 0.1Msodium nitrite is equivalent to 16.52mg of C9H11NO2.

Expert Committee:(PA1)Pharmaceutical Analysis 1

USP28–NF23Page 229

Phone Number:1-301-816-8379