How can I prepare the next eye drops? Nafluoresceine 25 mg OxybuprocaineHCl 40 mg boric acid 167 mg phenylmecuriborate Z.A.N. Water up to 10 ml

In the composition of this preparation, which, because of its narcotic properties, is loved by the ophthalmologists for detecting a foreign object in the eye, it puts a pH incompatibility. After all, Nafluoresceine requires an alkaline ph in order to avoid precipitation of fluorescein, while oxybuprocaine for its stability desires a slightly acidic ph (presence of boric acid!).

It is therefore necessary to find a compromise with priority for stability. Irrevocably, a precipitate of fluorescein will be formed. Fortunately, there is a possibility to keep the formed fluorescein in solution through complex formation with povidone or PVP. A significant amount of 2 G is required. This makes the solution rather viscous so that filtration through a membrane filter becomes very difficult. Oxybuprocaine can be sterilized according to the literature data using heat. In order to minimize degradation, preference is given to the method of Deussen, with the necessary precautions taken.

Method:
The losses oblige us to make 10% excess to be able to deliver 10 ml.

take a 15 ml dry bottle and bring the PVP together with the Nafluoresceine (dry). Stop the bottle and mix both by shaking. Dissolve oxybuprocaine and boric acid in 11 ml of phenyl mercuriborate solution (10 mg/100 ml) and add this solution in different portions to the vial. Shake after each addition. Let rest until all the clubbers are dissolved and a clear solution is obtained.

sterilize by autoclaving a collyrevial and the corresponding design (or take a pre-sterilized collyrevial). Transfer the solution into a syringe, remove the partly sucked-in air and place in the filter holder a front filter (glass filter). Place the filter holder on the syringe and weigh the whole.

apply the sterilized and dry collyrevial as well as the design in the LAF cabinet. In the LAF case, filter 10 g of the solution by the filter in the eye dropper vial. Determine the weight decrease of the syringe by reweighing. Close the collyrevial and turn the cap slightly open. Apply the Deussen method.