Question
Posted on: March 6 2013We have problems with following preparation: Metronidazole 1 g lactic acid 1.5 g eucerine, Aqua (25%) AD 100 g
After preparation, I do the ointment 3 times through the ointment mill and every time Pati ë NT come back a few days later because there are needles formed in the CR è me, which then go away by using the ointment grinder.
Answer
It is clear that this is a problem of solubility. Lactic acid is added to increase the solubility of metronidazole by salt formation. But the solubility of the lactate is nowhere to be found. In each case the concentration becomes relatively high with only 25 g water in the CR è me. That is why I propose to bring the water content to 40%. If the W/O cr è me seem unstable, you can always add 1 g of Arlacel or Span.