U.S. PHARMACOPEIA

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Tobramycin Ophthalmic Ointment
» Tobramycin Ophthalmic Ointment contains the equivalent of not less than 90.0 percent and not more than 120.0 percent of the labeled amount of tobramycin (C18H37N5O9).
Packaging and storage— Preserve in collapsible ophthalmic ointment tubes.
Identification— Vigorously shake by mechanical means a quantity of Ophthalmic Ointment, equivalent to about 3 mg of tobramycin, with 2 mL of chloroform. Add 1 mL of water, shake vigorously by mechanical means for 1 minute, and centrifuge for 15 minutes: the clear upper, aqueous layer so obtained meets the requirements of Identification test A under Tobramycin.
Sterility 71 It meets the requirements when tested as directed for Membrane Filtration under Test for Sterility of the Product to be Examined..
Minimum fill 755: meets the requirements.
Water, Method I 921: not more than 1.0%, 20 mL of a mixture of toluene and methanol (7:3) being used in place of methanol in the titration vessel.
Metal particles 751: meets the requirements.
Residual solvents 467: meets the requirements.
(Official January 1, 2007)
Assay—
Mobile phase, 2,4-Dinitrofluorobenzene reagent, Tris(hydroxymethyl)aminomethane reagent, Standard preparation, Resolution solution, and Chromatographic system— Proceed as directed in the Assay under Tobramycin.
Assay preparation— Transfer an accurately weighed portion of Ophthalmic Ointment, equivalent to about 4.5 mg of tobramycin, to a separator, add 50 mL of ether, and extract with four 20- to 25-mL portions of water. Combine the water extracts in a 100-mL volumetric flask, dilute with water to volume, and mix.
Derivatization procedure— Proceed as directed in the Assay under Tobramycin, except to use 15.0 mL of Assay preparation instead of 4.0 mL.
Procedure— Proceed as directed in the Assay under Tobramycin. Calculate the quantity of tobramycin (C18H37N5O9), in mg, in the portion of Ophthalmic Ointment taken by the formula:
(4 / 150)(CE)(rU / rS),
in which the terms are as defined therein.
Auxiliary Information— Staff Liaison : Brian D. Gilbert, Ph.D., Scientist
Expert Committee : (MDANT05) Monograph Development-Antibiotics
USP29–NF24 Page 2160
Phone Number : 1-301-816-8223