**5. Conclusions**

The present findings support the use of transdermal fentanyl patches as a method to provide long-lasting analgesia in NZW rabbits. Depending on how long potent analgesia is required, either the neck or the outer surface of the ear are suitable for patch application. Summarizing, the administration of the patch can simplify postoperative pain managemen<sup>t</sup> in laboratory rabbits and improve animal welfare in sense of the 3R.

**Author Contributions:** Conceptualization, V.M., C.S., H.R. and S.Z.; methodology, V.M., C.v.D., A.H. and S.Z.; validation, V.M., C.v.D. and A.H.; formal analysis, V.M., C.v.D. and A.H.; investigation, V.M., C.v.D., A.H. and S.Z.; resources, S.Z.; data curation, V.M. and S.Z.; writing—original draft preparation, V.M.; writing—review and editing, V.M., C.v.D., A.H., C.S., H.R. and S.Z.; visualization, V.M. and A.H., supervision, C.S., H.R. and S.Z.; project administration, V.M. and S.Z.; funding acquisition, S.Z. All authors have read and agreed to the published version of the manuscript.

**Funding:** Funding for this study was provided by the AO Foundation (grant number FS2017\_02). No external funds were received in support of this work.

**Acknowledgments:** The authors would like to thank the whole team of the Preclinical Facility at the AO Research Institute Davos for their support with the implementation of the project.

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