## 3 Results and Discussion
### Compatibility between Raw Materials  
The DSC analysis of physical mixtures of the selected raw materials was performed to assess the compatibility between them. The physical mixtures of raw materials were obtained by combining each recipient with an API (50:50 ratio) making a total of 15 mixtures. Figure 4 shows three DSC thermograms obtained for the physical mixtures of MCC with  
Figure 3: STA thermograms of active pharmaceutical ingredients (APIs): (**a**) Esomeprazole Mg 2H2O (a.1—Mass Change: \(-\)5.19%; a.2—Mass change: \(-\)33.46%; a.3—Residual Mass: 60.43%), (**b**) Esomeprazole Mg 3H2O (b.1—Mass Change: \(-\)7.73%; b.2—Mass change \(-\)29.83%; b.3—Residual Mass: 58.59%) and (c) Ondansetron (c.1—Mass Change: \(-\)9.59%; c.2—Mass change: \(-\)72.02%; c.3—Residual Mass: 17.94%).  
\begin{table}
\begin{tabular}{c c c} \hline \hline  & **Melting Point (T \({}^{\circ}\)C) 1** & **Decomposition (T \({}^{\circ}\)C)** \\ \hline MCC & 338 & 300 \\ PVP K17 & 72 & 400 \\ PVP K25 & 82 & 400 \\ PVP K90 & 73 & 400 \\ PVA Mw30 & 180 & 280 \\ Esomeprazole Mg (2H2O) & 164 & 200 \\ Esomeprazole Mg (3H2O) & 149 & 180 \\ Ondansetron & 181 & 220 \\ \hline \hline \end{tabular} \({}^{\dagger}\) Peak temperature of endothermic effect.  
\end{table}
Table 3: Melting temperature and thermal stability of raw materials as determined by STA analysis.  
each API. The assessment of their compatibility was made by comparing thermograms of each material with the ones obtained for physical mixtures. When mixture show a similar thermal behaviour to the ones observed when ingredients are analysed individually, this suggests their compatibility.  
In the case of MCC analysis with each API, the obtained thermogram represents mainly the addition of the ones obtained for each individual ingredient. This means that there is no relevant chemical or physical interaction between these ingredients up to the studied temperature (i.e., 200 \({}^{\circ}\)C) (Figure 4). Considering the mixtures obtained with PVPs (K17, K25 and K90) and both esomeprazole Mg 2H2O, 3H2O, there were no notable changes in the thermograms, indicating no significant physical and/or chemical interactions in the mixtures up to the studied temperature (200 \({}^{\circ}\)C) (Supplementary Materials--Figures S9-S11). However, in the case of ondansetron, the mixture thermograms were clearly not additive in relation to the ones obtained for each individual ingredient (Figure 5).  
For all PVPs studied, there was a temperature deviation for the first endothermic effect and a temperature deviation along with a peak widening in the second endothermic effect. These results suggested some extent of incompatibility between ondansetron and PVPs. Incompatibility of APIs with PVPs was also previously reported by [PERSON] et al., for ketoprofen and PVP K-30 [42]. Finally, the DSC thermograms of the individual ingredients were compared with the thermograms of the PVA Mw30 mixtures to further evaluate the compatibility between them. An additive effect of the peaks was observed, suggesting that there was no noticeable incompatibility between materials. The DSC thermograms of all mixtures revealed an additive effect of the peaks in relation to the single raw materials (Supplementary Materials--Figures S9-S11).  
Figure 4: DSC thermograms of single materials (MCC, esomeprazole Mg 2H2O, esomeprazole Mg 3H2O and ondansetron) and physical mixtures of MCC and APIs (50:50).