**5. Conclusions**

The administration of lipid vesicles containing DEX offered the advantage of a prolonged release of the drug and was confirmed to have an extended antinociceptive effect in the hot plate test in rats.

The results obtained in this study provide important perspectives for fundamental medicine—through the design and characterization of new nanoparticles incorporating DEX —as well as for medical practice—through the possibility of using, after multiple subsequent studies, such nanoparticulate formulations—with prolonged release of the nonsteroidal anti-inflammatory drug in pain therapy. The reduced frequency of administration shall increase patient compliance, and consequently, the therapy outcome.

**Author Contributions:** Conceptualization and methodology, L.M.-T., D.A.P. and E.G.P.; data analysis, M.B. and D.A.P.; investigation, L.M.-T., D.A.P., L.H., A.-M.P., B.R.B. and E.G.P.; writing—original draft preparation, M.B., D.A.P., L.H., A.-M.P., B.R.B., L.A.D. and E.G.P.; writing—review and editing, L.M.-T., M.B. and L.A.D.; supervision and project administration, L.M.-T. and E.G.P. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by "Grigore T. Popa" University of Medicine and Pharmacy, Iasi, Romania, Internal Research Grant number 16407—Project director Liliana Mititelu-Tartau.

**Institutional Review Board Statement:** The protocol of the study was approved (Protocol No. 19157/19.10.2009) by the Ethic Committee on Research of 'Grigore T. Popa' University of Medicine and Pharmacy, in Iasi, Romania, according to the European Ethical Regulations and to the guidelines of IASP Committee for Research and Ethical Issues.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest.
