Packaging and storage—
Preserve in collapsible ophthalmic ointment tubes.
Thin-layer chromatographic identification test á201BNPñ:
meets the requirements.
Water,Method Iá921ñ:
not more than 0.5%,20mLof a mixture of toluene and methanol (7:3)being used in place of methanol in the titration vessel.
Assay for neomycin—
Proceed as directed under
Antibiotics—Microbial Assays á81ñ,using an accurately weighed portion of Ophthalmic Ointment shaken in a separator with about 50mLof ether,and extracted with four 20-mLportions of
Buffer No.3.Combine the aqueous extracts,and dilute with
Buffer No.3to an appropriate volume to obtain a stock solution.Dilute this stock solution quantitatively and stepwise with
Buffer No.3to obtain 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 under
Antibiotics—Microbial Assays á81ñ,using an accurately weighed portion of Ophthalmic Ointment shaken with about 50mLof ether in a separator,and extracted with four 25-mLportions of
Buffer No.6.Combine the aqueous extracts,and dilute with
Buffer No.6to an appropriate volume to obtain a stock solution.Dilute this stock solution quantitatively and stepwise with
Buffer No.6to obtain a
Test Dilution having a concentration assumed to be equal to the median dose level of the Standard (10Polymyxin 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 bacitracin—
Proceed as directed under
Antibiotics—Microbial Assays á81ñ,using an accurately weighed portion of Ophthalmic Ointment shaken with about 50mLof ether in a separator,and extracted with four 25-mLportions of 0.01Nhydrochloric acid.Combine the acid extracts,and dilute with 0.01Nhydrochloric acid to an appropriate volume to obtain a stock solution.Dilute this stock solution quantitatively and stepwise with
Buffer No.1to obtain a
Test Dilution having a concentration assumed to be equal to the median dose level of the Standard (1.0Bacitracin Unit per mL).
[NOTE—If the stock solution has a concentration of less than 100Bacitracin Units per mL,add additional hydrochloric acid to each test dilution of the Standard to obtain the same concentration of hydrochloric acid as the
Test Dilution.
]