The effect of excipients on the stability and phase transition rate of xylazine hydrochloride and zopiclone

- IR spectroscopy showed absence of chemical interaction between excipients and drug.
- In thermal analysis physical interaction between excipients and drug was identified.
- Some excipients promoted but some reduced stability of the API unstable polymorph.
- Phase transition rate of API depended on the type and the amount of excipient added.