Gentamicin Eye Drops

General Notices

Action and use

Aminoglycoside antibacterial.

Definition

Gentamicin Eye Drops are a sterile solution of Gentamicin Sulfate in Purified Water.

The eye drops comply with the requirements stated under Eye Preparations and with the following requirements.

Identification

A. Carry out the method for thin-layer chromatography, Appendix III A, using the following solutions.
(1) Dilute a volume of the eye drops, if necessary, with sufficient water to produce a solution containing the equivalent of 0.3% w/v of gentamicin.
(2) 0.5% w/v of gentamicin sulfate BPCRS in water.
chromatographic conditions
(a) Use as the coating silica gel (Merck silica gel 60 plates are suitable).
(b) Use the mobile phase as described below.
(c) Apply 10 µL of each solution.
(d) Develop the plate to 15 cm.
(e) After removal of the plate, allow it to dry in air, spray with ninhydrin solution R1 and heat at 105° for 2 minutes.
mobile phase

The lower layer obtained by shaking together equal volumes of 13.5m ammonia, chloroform and methanol and allowing to separate.

confirmation

The three principal spots in the chromatogram obtained with solution (1) correspond to the three principal spots in the chromatogram obtained with solution (2).

B. In the test for Composition of gentamicin sulfate, the retention times of the four principal peaks in the chromatogram obtained with solution (1) correspond to those of the four principal peaks in the chromatogram obtained with solution (2).

Tests

Composition of gentamicin sulfate

Carry out the method for liquid chromatography, Appendix III D, using the following solutions.

(1) Add 5 mL of methanol to 10 mL of a solution prepared by diluting a suitable volume of the eye drops with water to contain the equivalent of 0.045% w/v of gentamicin. Swirl and add 4 mL of phthalaldehyde reagent, mix and add sufficient methanol to produce 25 mL, heat in a water bath at 60° for 15 minutes and cool. If the solution is not used immediately, cool to 0° and use within 4 hours.
(2) Prepare in the same manner as solution (1) but using 10 mL of a 0.065% w/v solution of gentamicin sulfate BPCRS in place of 10 mL of the preparation being examined.
chromatographic conditions
(a) Use a stainless steel column (12.5 cm × 4.6 mm) packed with end-capped octadecylsilyl silica gel for chromatography (5 µm) (Hypersil ODS and Kromasil C18 are suitable).
(b) Use isocratic elution and the mobile phase described below.
(c) Use a flow rate of 1.5 mL per minute.
(d) Use an ambient column temperature.
(e) Use a detection wavelength of 330 nm.
(f) Inject 20 µL of each solution.
mobile phase

0.025m sodium heptanesulfonate monohydrate in a mixture of 5 volumes of glacial acetic acid, 25 volumes of water and 70 volumes of methanol.

When the chromatograms are recorded under the prescribed conditions the retention time of component C2 is 10 to 20 minutes. The retention times relative to component C2 are: about 0.13 (reagent); about 0.27 (component C1); about 0.65 (component C1a); about 0.85 (component C2a).

system suitability

The test is not valid unless, in the chromatogram obtained with solution (2), the resolution factor between the peaks due to components C2a and C2 is at least 1.3.

limits

Using the chromatogram obtained with solution (1) calculate the percentage content of components C1, C1a, C2 and C2a in the eye drops by normalisation. The proportions are within the following limits:

C1, 25.0 to 50.0%;

C1a, 10.0 to 35.0%;

C2 plus C2a, 25.0 to 55.0%.

Assay

Dilute a volume of the eye drops containing the equivalent of 15 mg of gentamicin to 50 mL with sterile phosphate buffer pH 8.0 and dilute 10 mL of the resulting solution to 50 mL with the same solvent. Carry out the microbiological assay of antibiotics, Appendix XIV A. The precision of the assay is such that the fiducial limits of error are not less than 95% and not more than 105% of the estimated potency.

Calculate the content of gentamicin in the eye drops, taking each 1000 IU found to be equivalent to 1 mg of gentamicin. The upper fiducial limit of error is not less than 90.0% and the lower fiducial limit of error is not more than 120.0% of the stated content.

Labelling

The quantity of active ingredient is stated in terms of the equivalent amount of gentamicin.