## 4 Conclusions  
ETB-NE was formulated and optimized using percentages of oil, S\({}_{\text{mix}}\), and water as the independent factors, and PS and PDI as responses. The optimized ETB-NE contained oil, S\({}_{\text{mix}}\), and water in concentrations of 11.5, 38, and 50%, respectively. The optimized ETB-NE had satisfactory droplet size and PDI close to the predicted values. Meanwhile, the zeta potential value was \(-\)10.9 \(\pm\) 1.01 mV for the ETB-NE. The in vitro drug release was significantly higher from the ETB-NE than from the aqueous dispersion of the drug. The nanoemulsion gel prepared from the ETB-NE was characterized for pH, viscosity, drug content, and percentage entrapment efficiency. Further, significantly higher in vitro skin permeation was observed from the ETB-NEG. The non-irritant and non-toxicity of ETB-NEG formulation in rat skin were confirmed by the histopathology study. In the in vivo evaluation of analgesic activity, MPA was significantly higher for ETB-NEG (47.09% after 60 min), demonstrating its enhanced analgesic activity compared to pure drug. The formalin-induced acute inflammatory pain study in rats also demonstrated higher analgesia for the ETB-NEG sample, and in both in acute and late phases. Similarly, the in vivo anti-inflammatory activity was more for ETB-NEG and the percentage inhibition was 78.4 \(\pm\) 3.5% at 8 h. Thus, the results of the studies proved ETB-NEG to be superior to the pure drug for topical delivery. The study encourages future research in this area for further development of ETB-NEG to a clinically successful formulation.  
Figure 6: Photomicrograph showing the **(A)** untreated control group of rat skin: this is formed of two layers; epidermis (Ep) and dermis. The epidermal–dermal junction shows many dermal papillae; (**B**) formalin treated rat skin as a positive control group showing the thickened epidermis (Ep), invaginated keratin layer into the epidermis (thick arrow) and intercellular edema (star); (**C**) Blank NEG treated rat skin; and (**D**) ETB-NEG treated rat skin showing the moderately thickened epidermis (Ep) and the presence of little reaction (\(\dagger\)). H&E 400\(\times\).  
**Author Contributions:** Conceptualization, N.A.A., J.A. and S.M.; Data curation, N.A.A., S.K., J.A., M.S.A., K.M.H., R.A.S., B.G.E., Y.R., H.Z.A., N.A. and S.M.; Formal analysis, N.A.A., S.K., M.S.A., K.M.H., R.A.S., B.G.E., H.Z.A. and S.M.; Investigation, J.A., R.A.S., Y.R. and H.Z.A.; Methodology, N.A.A., S.K., M.S.A., K.M.H., R.A.S., B.G.E., Y.R. and N.A.; Software, K.M.H.; Writing--original draft, S.K., M.S.A., Y.R. and S.M.; Writing--review & editing, J.A., B.G.E., H.Z.A. and N.A. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This project was funded by the Deanship of Scientific Research (DSR) at King Abdulaziz University, Jeddah, under grant no. (RG-11-166-38).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The data presented in this study are available in article.  
**Acknowledgments:** The authors acknowledge with thanks DSR for technical and financial support.  
**Conflicts of Interest:** The authors declare no conflict of interest.