Question
Posted on: March 6 2013Problem of crystallization of NaCl in eye ointment!
I already make a few months sterile eye Ointment 5% NaCl, Pati & Eumlnt complains (almost) always of grain feeling. I loose 0.5 g NaClop in 2g water for injection and Mount 8g Ung. Oculare in drying oven (150 ° C 1u). The solution is filtered by a sterilizing membrane filter and in the LAF case mixed with the sterilized eye ointment base. What can I improve or what can be the cause of precipitation (conc NaCl?)?
Answer
At the concentration NaCl it will not lie because the amount of water is ample to dissolve 0.5 g NaCl. But the precipitation is perhaps due to evaporation of a certain amount of solvent when adding the solution to the base, which may have been insufficient cooled down. In A first reaction it is perhaps thought that adding to a not yet firm ointment basis facilitates the intake of the water under the form of a W/O emulsion. This reasoning is not wrong, but it is better not applied here.
so we recommend to allow the sterilized eye ointment base to cool completely to room temperature.
I must also point to the dead volume of the filter used. Therefore, it is best to prepare a double quantity of NaCl solution, which is then filtered by a sterilized membrane filter where the first drops are collected in a beaker. From this point onwards, 2ml is filtered into the eye ointment base.