In this preparation the cream colors completely brown-Rozig. Hydroquinc 5% Tretinoin acid 0.05% erythromycin 1g Beeler Base AD 50g

If you enter hydroquinone in the search box of the question-boxes, you will get a series of questions with information about the preparation, about which you ask. I think that especially the following question is useful:   regularly i get a prescription on which the following preparation, however, it appears to be only a 14 days shelf life, do you know why and could I improve something in the formula?

I fear, however, that the stability of your composition is hampered by the presence of erythromycin that reacts Alcalisch. The combination is not ideal and if Antioxydantia does not offer a solution then it will have to be considered to process erythromycin in a separate cream. The excipient seems OK.