Packaging and storage—
Preserve in tight, light-resistant containers in a cool place or at controlled room temperature. The containers or individual cartons are sealed and tamper-proof so that sterility is assured at time of first use.
Identification—
Transfer a quantity of Ophthalmic Suspension, equivalent to about 2.5 mg of dexamethasone, to a suitable test tube, add 5 mL of chloroform, mix, and centrifuge. Apply 25 µL of the lower chloroform layer and 25 µL of a Standard solution of
USP Dexamethasone RS in chloroform containing 500 µg per mL to a suitable thin-layer chromatographic plate (see
Chromatography 
621
) coated with a 0.25-mm layer of chromatographic silica gel. Allow the spots to dry, and develop the chromatogram in a solvent system consisting of a mixture of chloroform and diethylamine (2:1) until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the developing chamber, mark the solvent front, and allow the solvent to evaporate. Locate the spots on the plate by examination under short-wavelength UV light: the
RF value of the principal spot obtained from the test solution corresponds to that obtained from the Standard solution.
Sterility 71—
It meets the requirements when tested as directed for
Membrane Filtration under
Test for Sterility of the Product to be Examined.
Assay for neomycin—
Proceed as directed for neomycin under
Antibiotics—Microbial Assays 81, using an accurately measured volume of Ophthalmic Suspension, freshly mixed and free from air bubbles, 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.
Assay for polymyxin B—
Proceed as directed for polymyxin B under
Antibiotics—Microbial Assays 81, using an accurately measured volume of Ophthalmic Suspension, freshly mixed and free from air bubbles, 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. Add to each test dilution of the Standard a quantity of
USP Neomycin Sulfate RS, dissolved in
Buffer No. 6, to obtain the same concentration of neomycin as is present in the
Test Dilution.
Assay for dexamethasone—
Standard preparation—
Dissolve an accurately weighed quantity of
USP Dexamethasone RS in
Mobile phase to obtain a solution having a known concentration of about 0.12 mg per mL.
Assay preparation—
Dilute an accurately measured volume of freshly mixed Ophthalmic Suspension quantitatively with
Mobile phase to obtain a solution containing about 0.12 mg of dexamethasone per mL.
Procedure—
Proceed as directed for
Procedure in the
Assay for dexamethasone under
Neomycin and Polymyxin B Sulfates and Dexamethasone Ophthalmic Ointment. Calculate the quantity, in mg per mL, of C
22H
29FO
5 in the Ophthalmic Suspension taken by the formula:
(CL / D)(rU / rS),
in which
L is the labeled quantity, in mg per mL, of dexamethasone in the Ophthalmic Suspension,
D is the concentration, in mg per mL, of dexamethasone in the
Assay preparation based on the labeled quantity in the Ophthalmic Suspension and the extent of dilution, and the other terms are as defined therein.
