Packaging and storage—
Preserve in tight, light-resistant containers. The containers or individual cartons are sealed and tamper-proof so that sterility is assured at time of first use.
Assay for neomycin—
Proceed as directed under
Antibiotics—Microbial Assays 
81
, using an accurately measured volume of Otic Solution diluted quantitatively and stepwise with
Buffer No. 3 to yield a
Test Dilution having a concentration assumed to be equal to the median dose level of the Standard (1.0 µg of neomycin per mL).
Assay for polymyxin B—
Proceed as directed under
Antibiotics—Microbial Assays 81, using an accurately measured volume of Otic Solution diluted quantitatively and stepwise with
Buffer No. 6 to yield a
Test Dilution having a concentration assumed to be equal to the median dose level of the Standard (10 Polymyxin B Units per mL). Add to each test dilution of the Standard a quantity of Neomycin Standard, dissolved in
Buffer No. 6, to obtain the same concentration of neomycin present in the
Test Dilution.
Assay for hydrocortisone—
Mobile phase
, Standard preparation, and Chromatographic system—Prepare as directed in the Assay for hydrocortisone under Neomycin and Polymyxin B Sulfates, Bacitracin Zinc and Hydrocortisone Ophthalmic Ointment.
Assay preparation—
Transfer 3.0 mL of Otic Solution to a 200-mL volumetric flask, dilute with a mixture of methanol and water (1:1) to volume, and mix.
Procedure—
Proceed as directed for
Procedure in the
Assay for hydrocortisone under
Neomycin and Polymyxin B Sulfates, Bacitracin Zinc and Hydrocortisone Ophthalmic Ointment. Calculate the quantity, in mg, of C
21H
30O
5 in each mL of the Otic Solution taken by the formula:
(66.67C)(rU / rS),
in which
C is the concentration, in mg per mL, of
USP Hydrocortisone RS in the
Standard preparation, and
rU and
rS are the peak responses obtained from the
Assay preparation and the
Standard preparation, respectively.
