How to make best next suppositories

This is compound, which does not seem easily feasible. For me, the big culprit is acetylsalicylic acid.  

Reactions of acetaminophen in pharmaceutical dosage forms: Its proposed acetylation by acetylsalicylic acid Keywords: Acetaminophen reactions — dosage forms; Aspirin — acetaminophen acetylation; Codeine PO ₄ , caffeine effect — acetaminophen stability; Humidity effect — acetaminophen stability; Abstract Acetylation of acetaminophen (paracetamol) by acetylsalicylic acid to O, N -diacetyl- P -aminophenol (DAPAP) was not evident in experimental pharmaceutical dosage forms. DAPAP, which was found to be present in small quantities in commercial grade acetaminophen, is unstable in pharmaceutical preparations. The destruction of DAPAP increases rapidly with the temperature and moisture content of the system. Solid DAPAP seems to exist in at least two forms, as shown by their IR spectra. The observed color drops of suspensions containing acetaminophen is mainly due to the oxidative degradation of the liberated P -aminophenol. The presence of codeine phosphate and caffeine seems to enhance the color deterioration of solid preparations containing acetaminophen kept at 45 ° and in a humid atmosphere. It is recommended that moisture be excluded, as much as possible, from such preparations. In the British Pharmaceutical Codex, the interaction Paracetamol & ASA is also treated. My attention goes to: "The importance of minimising the moisture content of products containing paracetamol was emphasized".     Preparation method (with help of pharmacist Heleen Maus)   The conclusion is that the reaction between these two components is avoided. For this we can divide the amount of suppository mass into two parts and melt each separately. At one we add the ASA as fine powder and mix to homogeneous. In the second molten part, we add the other ingredients mixed together into a homogeneous mixture L. A second important point is the temperature control. We therefore ensure that both parts have a temperature     of up to 35 à   37 °C   before joining the ASA part at the second part.   note   an antioxidant from the range of the oil-soluble can be added (see Website Qualenica > Recipe Helpdesk >   Pharmaceutical preparation)   to protect Promethazine, which Oxidizable product. A simultaneous addition of Na2EDTA (0.1%) may also be considered because metal ions are catalysts of oxidation reactions.