## 4 Conclusions  
Several ingredients (active and non-active) were characterised in terms of moisture content, flowability, particle size, morphology and X-RPD pattern. Its compatibility and stability were studied by the thermal methods of analysis, and X-ray diffraction patterns.  
The values of moisture contents obtained using both techniques (i.e., loss on drying and thermal analysis) agreed except for MCC, the differences of which were related to environmental analysis conditions.  
In the case of some binary mixtures, changes in the profile of thermograms (STA and DSC) indicate the production of some interactions as a function of heating. That was the case of mixtures of PVPs with ondansetron. For the other mixtures studied, no interactions were observed up to 200 \({}^{\circ}\)C.  
Among all the ingredients selected, the PVPs (K17, K25 and K90) have the best characteristics to incorporate both forms of esomeprazole Mg in a formulation to produce extrudates. These excipients have a high thermal stability (up to 400 \({}^{\circ}\)C), and they begin to soften below 100 \({}^{\circ}\)C, which may be advantageous because the extrusion process should be carried out below 180 \({}^{\circ}\)C to ensure the thermal stability of the APIs. At the required temperature for the extrusion process, the PVPs are expected to produce a paste-like phase that allows the homogeneous incorporation of the APIs and an adequate consistency of the extruded product extrusion. For ondansetron, due to the possible incompatibility observed in the thermal analysis of physical mixtures with PVPs, PVA Mw 30 could be an alternative to produce extrudates. However, further studies should be conducted, or other ingredients such as some partial cross-linked hydrogels (e.g., hyaluronic acid or its derivates, Pluronics(r), Buenos Aires, Argentina) may be considered to produce 3D-printed oral formulations.  
Figure 5: DSC thermograms of single materials and physical mixtures between ondansetron and PVPs (K17, K25 and K90).  
Supplementary Materials:The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app122010585/s1](https://www.mdpi.com/article/10.3390/app122010585/s1)]([https://www.mdpi.com/article/10.3390/app122010585/s1](https://www.mdpi.com/article/10.3390/app122010585/s1)), Figure S1: Diffractogram of microcrystalline cellulose (MCC) analysis by X-RPD technique, Figure S2: Microcrystalline cellulose (MCC) TG/DSC (STA) thermogram; Figure S3: Diffractograms of PVP K25 (a) and PVP K90 (b) analysis by X-RPD technique; Figure S4: PVP K17 (a), PVP K25 (b) and PVP K90 (c) TG/DSC (STA) thermograms; Figure S5. Diffractogram of PVA Mw30 analysis by X-RPD technique; Figure S6: PVA Mw30 TG/DSC (STA) thermogram; Figure S7: Diffractograms of esomeprazole Mg 2H2O and 3H2O analysis by X-RPD technique; Figure S8: Ondansetron TG/DSC (STA) thermogram; Figure S9: DSC mixtures thermograms of PVP K17 with esomeprazole: esomeprazole Mg 2H2O (a) and esomeprazole Mg 3H2O (b); Figure S10 : DSC mixtures thermograms of PVP K25 with esomeprazole: esomeprazole Mg 2H2O (b); Figure S11: DSC mixtures thermograms of PVP K90 with esomeprazole: esomeprazole Mg 2H2O (a) and esomeprazole Mg 3H2O (b); Figure S12: DSC mixtures thermograms of PVA Mw30 with different APIs: esomeprazole Mg 2H2O (a); esomeprazole Mg 3H2O (b) and ondansetron (c).  
Conceptualisation, C.M.L. and J.C.; Investigation, M.F. and H.G.; Methodology, C.M.L. and J.C.; Project administration, C.M.L. and J.C.; Supervision, C.M.L. and J.C.; Writing--original draft, M.F.; Writing--review and editing, C.M.L., J.F.P. and J.C. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The authors would like to thank the suppliers of APIs, Minakem(r) (France), who provided esomeprazole magnesium dihydrate micronucleised EUR, and Zim Laboratories Limited (India), who provided both esomeprazole magnesium trihydrate USP and ondansetron hydrochloride USP.  
The authors declare no conflict of interest.