Benzocaine Topical Solution
» Benzocaine Topical Solution is a solution of Benzocaine in a suitable solvent. It contains not less than 90.0 percent and not more than 110.0 percent of the labeled amount of C9H11NO2. It contains a suitable antimicrobial agent.
Packaging and storage Preserve in tight containers, protected from light, and avoid prolonged exposure to temperatures exceeding 30.
Identification Transfer an amount of Topical Solution, equivalent to about 5 mg of benzocaine, to a small beaker, add 20 mL of 0.5 N hydrochloric acid, warm gently to disperse, cool, and filter. To 10 mL of the filtrate add 5 drops of sodium nitrite solution (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.
Assay Transfer an accurately weighed portion of Topical Solution, equivalent to about 200 mg of benzocaine, to a 250-mL beaker. Add 50 mL of water and 5 mL of hydrochloric acid, and stir. 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. Perform a blank determination, and make any necessary correction. Each mL of 0.1 M sodium nitrite is equivalent to 16.52 mg of C9H11NO2.
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USP35NF30 Page 2322