Benzocaine Otic Solution
» Benzocaine Otic Solution contains not less than 90.0 percent and not more than 110.0 percent of the labeled amount of C9H11NO2.
Packaging and storage— Preserve in tight, light-resistant containers.
Identification— Transfer a volume of Otic Solution, equivalent to about 2.5 mg of benzocaine, to a small beaker, add 10 mL of water, and dissolve with the aid of a few drops of 3 N hydrochloric acid. Add 5 drops of sodium nitrite solution (1 in 10), then 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 Salmonella species and Escherichia coli and for absence of Staphylococcus aureus and Pseudomonas aeruginosa; the total aerobic microbial count is less than 100 cfu per mL.
Assay— Transfer an accurately measured volume of Otic Solution, equivalent to about 400 mg of benzocaine, to a beaker, add 150 mL of cold 1.6 N hydrochloric acid, and stir until a fine dispersion is obtained. 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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61 Radhakrishna S Tirumalai, Ph.D.
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USP32–NF27 Page 1643