» Benzocaine Cream contains not less than 90.0 percent and not more than 110.0 percent of the labeled amount of C9H11NO2 in a suitable cream base.
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 50 mg of benzocaine, in a small beaker, add 20 mL of 0.5 N hydrochloric acid, warm gently to disperse the Cream, cool, and filter. To 10 mL of the filtrate add 5 drops of a solution of sodium nitrite (1 in 10) and 2 drops of methyl red TS, and neutralize with 1 N sodium hydroxide. Add 2 mL of a solution of 100 mg of 2-naphthol in 5 mL of 1 N sodium hydroxide: an orange-red precipitate is formed.
Microbial enumeration tests 61 and Tests for specified microorganisms 62 It meets the requirements of the tests for absence of Staphylococcus aureus and Pseudomonas aeruginosa.
Minimum fill 755: meets the requirements.
Assay Weigh accurately an amount of Cream, equivalent to about 200 mg of benzocaine, in a tared 250-mL beaker. Add 50 mL of water and 5 mL of 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 0.1 M sodium nitrite VS, determining the endpoint potentiometrically using a calomel-platinum electrode system. Each mL of 0.1 M sodium nitrite is equivalent to 16.52 mg of C9H11NO2.
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USP32NF27 Page 1641