Regularly i get a prescription on which the following preparation, however, it turns out to be only a 14 days shelf life, do you know why and would I be able to improve something in the formula?

In connection with the processing of Tretinoin I refer to the recently published article (Pharmaceutical Journal of Belgium) on the processing of hazardous raw materials in the pharmacy. In order to obtain a homogeneous distribution of tretinoin and due to the dangers caused by tretinoin powder, a hydrophilic concentrate is used. In This concentrate the Cetostearyl alcohol is found, which is part of an O/W cream. The combination of Hydroquinones with Cetomacrogolcreme is not the best choice as you can read under question 58. So better another base. As Antoxidans 1% ascorbic acid is recommended together with 0.1% Na2EDTA.