Question
Posted on: March 6 2013How to prepare best: Erythromycin 2% Salicylic acid 2% propylene glycol 10% Isopropanol 40% to 100 ml
This formulation provides a clear solution but is also stable and maintains its efficacy?
Answer
Within the period of 1 day, little unchanged erythromycin (EM) is recovered, since it is not stable in acidic middle. The pH Optimum is located at 8 to 8.5. At pH 7 and 25 ° C a loss of 15% is already found in weak acid center. It is advisable not to keep aqueous EM solutions in stock. An aqueous-alcoholic solution of 0.5 to 4% is stable for up to 2 months at 25 ° C.