I received a prescription for a "sterile" ear drop with chloramphenicol, hydrocortisone acetate and polymyxin. How to prepare?

The demand for sterile ear drops and the composition suggests that the ear drops are intended for the middle ear. This means that all products should be in solution and the solution sterile.     Therefore, hydrocortisone acetate should be replaced by hydrocortisonhemisuccinate, which dissolves in water at a light of PH. Maaar This product is no longer available in Belgiê. It could be replaced by dexamethasone-Na-phosphate. This way we get close to the composition of Polydexa ear drops. Just still lacking chloramfenicol. We prepare a separate sterile chloramphenicol ear droplet.   The prescribed amount is soluble in the boric acid-borax mixture. This solution can be filtered germ-free on a sterile 0.2 micrometer membrane filter in a pre-sterilized zentropvial. In turn, the customer can put a drop in the ear of both solutions.