PUBLICATIONS

Published: 19 May 2025, Nature Communications 2025; 16: 4659

A comparison of intramuscular and intranasal naloxone in reversal of fentanyl-induced apnea: a randomized, crossover, open-label trial.

A clinical review examining evidence comparing intramuscular and intranasal naloxone for the reversal of fentanyl-induced apnea, including findings from a randomized, crossover clinical study published in Nature Communications.

PUBLISHED: 13 JANUARY 2026, JOURNAL OF EMERGENCY MEDICAL SERVICES

EMS Clinical OPS: Intramuscular vs. Intranasal Naloxone

An EMS-focused review of intramuscular and intranasal naloxone, highlighting recent clinical evidence and considerations for naloxone administration in the field.

REFERENCES

  1. A comparison of intramuscular (Zimhi) and intranasal naloxone (Narcan) in reversal of fentanyl-induced apnea: a randomized, crossover, open-label trial. Published: 19 May 2025, Nature Communications 2025; 16: 4659 Maarten A. van Lemmen,  Monique van Velzen,  Elise Y. Sarton,  Albert Dahan, Marieke Niesters
  2. Fentanyl. United States Drug Enforcement Administration. Accessed December 22, 2021. https://www.dea.gov/factsheets/fentanyl
  3. Stanley T. H. The fentanyl story. J Pain. 2014;15(12):1215-1226. doi: 10.1016/j.jpain.2014.08.010
  4. Fatal Intoxication with Acetyl Fentanyl Journal of Forensic Sciences 61:p S276-S280, January 2016. | DOI: 10.1111/1556-4029.12953 Susan M. Cunningham Nabila A. Haikal James C. Kraner
  5. ZIMHI Prescribing information

INDICATION

ZIMHI is an opioid antagonist indicated for the emergency treatment of known or suspected opioid overdose, as manifested by respiratory and/or central nervous system depression in adult and pediatric patients. ZIMHI is intended for immediate administration as emergency therapy in settings where opioids may be present. ZIMHI is not a substitute for emergency medical care.

IMPORTANT SAFETY INFORMATION

As the duration of action of naloxone hydrochloride is shorter than many opioids, keep the patient under continued surveillance and administer repeated doses of naloxone using a new ZIMHI device, as necessary, while awaiting emergency medical assistance. Seek emergency medical assistance immediately after the first dose.
Reversal of respiratory depression caused by partial agonists or mixed agonists/antagonists, such as buprenorphine and pentazocine may be incomplete. Repeat doses of ZIMHI may be required.
Use in patients who are opioid dependent may precipitate opioid withdrawal. In neonates, opioid withdrawal may be life-threatening if not recognized and properly treated. Monitor for the development of signs and symptoms of opioid withdrawal.
Abrupt postoperative reversal of opioid depression may result in adverse cardiovascular (CV) effects. These events have primarily occurred in patients who had pre-existing CV disorders or received other drugs that may have similar adverse CV effects. Monitor these patients closely in an appropriate healthcare setting after use of naloxone hydrochloride.
After use, the ZIMHI needle is exposed until the safety guard is deployed. A needlestick injury could occur during use in emergency situations. In the event of accidental needlestick injury, medical attention should be sought.
The following adverse reactions were most commonly observed in ZIMHI clinical studies: dizziness, lightheadedness, nausea, and elevated bilirubin.
To report SUSPECTED ADVERSE REACTIONS, call 1-800-230-3935 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch

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