**5. Conclusions**

Mu receptor occupancy and plasma concentrations of naloxone following IM delivery of the drug have been investigated in rhesus monkeys. A significant correlation between percent RO and plasma naloxone level was found and confirms that higher doses of IM naloxone result in higher mu RO. These results support the notion that higher doses of IM naloxone may be useful for treatment of opioid overdoses due to potent synthetic opioids.

**Author Contributions:** Conceptualization, P.J.H.S. and R.B.M.; methodology, J.S., J.A., P.S.S., X.S., B.D.H., M.E.R., and A.R.S.; formal analysis, X.S., B.D.H., R.A.K., P.J.H.S., R.B.M., M.E.R., and A.R.S.; investigation, J.S., J.A., P.S.S., X.S., B.D.H., M.E.R., and A.R.S.; resources, P.J.H.S. and R.B.M.; data curation, X.S., B.D.H., M.E.R., A.R.S., R.A.K., and P.J.H.S.; writing—original draft preparation, P.J.H.S. and R.B.M.; writing—review and editing, all authors; supervision, P.J.H.S., R.B.M., and D.J.C.; project administration, P.J.H.S. and R.B.M.; funding acquisition, R.B.M. and P.J.H.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** The funding for this work was provided by Adamis Pharmaceuticals.

**Acknowledgments:** The authors would like to thank Bo Wen and Lu Wang of the University of Michigan Pharmacokinetic and Mass Spectrometry Core for assistance with the plasma naloxone assay.

**Conflicts of Interest:** D.J.C. and R.B.M. are employees of Adamis Pharmaceuticals who funded this study and provided naloxone.

#### **References**


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