Precipitation in the following composition: Prednisolone 1g chloramphenicol 4g propylene glycol 60g aqua destillata ad 200g

I do not think that the replacement of Prednisolone by the postphosphate ester Salt is a good solution for this preparation for external use!!

for Prednisolone is the solubility in water 1 on 1300 and chloramphenicol 1 on 400. The solubility of chloramphenicol in PG is 15 g per 100 ml. So for 4 G chloramphenicol We need 27 ml PG. We have 60 g but we have to take into account the dilution with water.
about the solubility of prednisolone in propylene glycol are no data to be found. The solubility in ethanol is 1 to 30. Given the solubility in a mixture of 2 cosolvents is often higher, I would suggest adding 60 g of antiseptic solution, in which the prednisolone is dissolved.
In A tarred beaker, 4 G of chloramphenicol is dissolved in 60 g of propylene glycol and the alcoholic solution of Prednisolone is added to this solution. After that, stirring slowly, water is added with attention to the formation of a cloudy. If a clouding occurs, the mixture of propylene glycol-antiseptic solution (1:1) is added until the cloudy has disappeared. Water is again diluted as above until 200 g of mixture is obtained with any additional mixture of propylene glycol-antiseptic solution.

There is also the simpler method of the preparation of a suspension in which 2 G of bentonite are dispersed in propylene glycol 60 g in which, and Prednisolone and Chloramphenicol were dissolved. Then, under hard stirring, diluted with water up to 200g.