Without evidence of benefit, an intervention should not be presumed to be beneficial or safe.

- Rogue Medic

The Myth that Narcan Reverses Cardiac Arrest


We are supposed to search for the potentially reversible causes of cardiac arrest and treat those causes. Since naloxone (Narcan) is the most familiar antidote out there, many people assume that we should be giving naloxone.

Narcan is in the ACLS (Advanced Cardiac Life Support) guidelines!

What do the ACLS guidelines actually state about naloxone?

Naloxone is a potent antagonist of the binding of opioid medications to their receptors in the brain and spinal cord. Administration of naloxone can reverse central nervous system and respiratory depression caused by opioid overdose. Naloxone has no role in the management of cardiac arrest.[1]


Naloxone has no role in the management of cardiac arrest.

Yes. Naloxone is in the ACLS guidelines, but the guidelines say naloxone is not for cardiac arrest.

But what if I really, really, really want to give Narcan?

We can give naloxone, but we shouldn’t pretend that we are following ACLS guidelines.

What about the Hs and Ts?

ACLS does state that we are supposed to consider the potentially reversible causes and to give a treatment that has the potential to improve the outcome. ACLS clearly states that naloxone is not one of those treatments.

Opioid overdose is a potentially reversible cause of cardiac arrest, but naloxone is not the recommended treatment. Opioids do not require administration of an antidote for resuscitation.

But at least Narcan is safe!

Opioid Depression
Abrupt reversal of opioid depression may result in nausea, vomiting, sweating, tachycardia, increased blood pressure, tremulousness, seizures, ventricular tachycardia and fibrillation, pulmonary edema, and cardiac arrest which may result in death (see PRECAUTIONS).


That is not a description of safe.

Safety depends on the context.

Yesterday I wrote about giving naloxone to an intubated patient who had good vital signs after a couple of minutes of chest compressions.[3] There are many ways that naloxone could have made things worse and only one way that it might have helped. That is not the kind of context where naloxone is safe. The medic got lucky.

Why go looking for trouble?

We get invited to enough trouble already.

In normal subjects anaesthetised with morphine and nitrous oxide,3 and in patients addicted to narcotics, pulse rate and blood pressure increase appreciably after reversal of the effects of opiates. Presumably naloxone antagonises opiate suppression of the sympathetic system resulting in a sudden increase in its activity.[4]


We could protect against this unwanted sympathetic stimulus by giving another drug, but how many drugs are we going to give to a patient who is already stable to try to produce a stable patient?

Clonidine might possibly be useful because it abolishes increases in pulse and blood pressure after reversal of opiate effects with naloxone.5 [4]


I am very aggressive in treating many things (e.g. high doses of nitrates for CHF, high doses of opioids and/or benzodiazepines), but these are supported by documentation of safety in the way that I use them.

Why go looking for trouble?

Naloxone has no role in the management of cardiac arrest.


[1] Opioid Toxicity
2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care
Part 12.7: Cardiac Arrest Associated With Toxic Ingestions
Free Full Text from Circulation

[2] NALOXONE HYDROCHLORIDE injection, solution
[Hospira, Inc.]

Adverse reactions
Opioid toxicity
FDA Label

[3] To Narcan or not Narcan
Tue, 11 Dec 2012
Rogue Medic

[4] Cardiac arrest after reversal of effects of opiates with naloxone.
Cuss FM, Colaço CB, Baron JH.
Br Med J (Clin Res Ed). 1984 Feb 4;288(6414):363-4. No abstract available.
PMID: 6419929 [PubMed – indexed for MEDLINE]

Free Full Text from Pubmed Central.



  1. Another great post. You may not realize it, but you are changing the way many of us practice. You got me with this one. While I long stopped using narcan in alive patients except in cases of hypoventilation in the opiate patient, I can’t tell you the number of times I have tossed in Narcan in a cardiac arrest without really considering what I have been doing or its effect. Keep up the great work

  2. How do you account for Saybolt et al. (2010) in the journal, Resuscitation? How do you account for studies with similar results? How do those studies affect your interpretation of your own leaps in logic, above? Essentially, you did not answer the question implied by the title of this particular article; you did not answer whether naloxone has a role in resuscitation of the patient in an opioid induced cardiac arrest. You did, however, rightly state that the use of naloxone carries with it certain risks. I would like to see further discussion on this topic.

  3. good read.
    check this article out


  4. Those of us in the medical field know that pretty much every prescription drug on the planet Earth lists simuliar precautions to naracan like the classic sz, coma, death. In addition those precautions mostly deal with someone who is heavily addicted to opioids and their withdrawl. What about the elderly patient who accidently overdosed, or the suicide attempt. If my family memeber overdoses on a opioid I hope I have a medic there that will give narcan. I would rather have my family member breathing on their own with a heartbeat, and worry about the effects of narcan later. I agree with a lot of what you wrote, I just do not agree with the statement “Naloxone has NO role in the management of cardiac arrest”. I will leave you with this question sir and I am interested to hear your answer. You walk in to find your 14 year old daughter that intentionally overdosed on morphine in a suicide attempt and she is in cardiac arrest. How would you treat her? Would you give her Narcan? I think you would. If so, then the words “no role” needs to be changed to “a very limited role”.

  5. Just playing devil’s advocate here…


    Fifteen of the 36 (42%) (95% confidence interval [CI]: 26-58) patients in cardiac arrest who received naloxone in the pre-hospital setting had an improvement in electrocardiogram (EKG) rhythm. Of the participants who responded to naloxone, 47% (95% CI: 21-72) (19% [95% CI: 7-32] of all study subjects) demonstrated EKG rhythm changes immediately following the administration of naloxone.
    Although we cannot support the routine use of naloxone during cardiac arrest, we recommend its administration with any suspicion of opioid use. Due to low rates of return of spontaneous circulation and survival during cardiac arrest, any potential intervention leading to rhythm improvement is a reasonable treatment modality.

    • Bill,

      I described the problems with that study in Naloxone in cardiac arrest with suspected opioid overdoses.

      There was only one survivor in this chart review.

      We do not know if that patient ever woke up.

      The authors claim that the naloxone is reversing histamine release.

      This claim demonstrates that the authors do not understand the effects of the epinephrine already given to every patient in their chart review.

      We should study naloxone in cardiac arrest, but we should not add it to what we give just because these authors are unreasonably optimistic.

      We could also justify singing silly songs during the attempt at resuscitation, based on the same rationale, but I doubt most families would appreciate that additional treatment.


  6. I was in hospital my heart stopped In ambulance but in hospital a nurse told me he was flushing my drip with water but was narcan and as it went through me my heart stopped again but I didn’t overdose on opiates it was one thing I NEVER WON’T TO GO THROUGH AGAIN

  7. I was in full blown cardiac arrest due to choking on some food
    When my wife found me i was blue and had been for around 15 mins. After administering cpr untill the medics arrived I was given a 2 mg dose of narcan. Shortly after I came to ND was starting tout come back. Saying this i do not do drugs and all my blood tests clearly showed I had none in my system. Was it a coincidence or did the narcan help Jumpstart me breathing. I know every article says it doesn’t so anything other then for opiate overdoses but something brought me back after 25 mins of not breathing.

    • If I start treating rats, these articles will be useful.

      I write about resuscitating humans.

      There are plenty of drugs that show benefit resuscitating rats.

      The problem is that the rat cardiac arrests are not remotely similar to human cardiac arrests.

      Are the rats having spontaneous cardiac arrests?


  8. I am currently reviewing the medical notes on a young 30 year old deceased male who was obese and cigarette smoker. He presented to his family doctor with chest pain, pallor, and sob. He was prescribed GTN and arranged for him to see a cardiologist. One month later he had a cardiac arrest from which he never recovered. The paramedics who attended the 911 call placed a tick in the box for drugs and as part of their ALS management i note that he received Narcan. Despite aggressive resuscitative measures this young man never recovered. The post mortem toxicology screen was negative and the only significant finding was an occluded LAD with no myocardial changes. Is there any evidence to suggest that Narcan compromises resuscitative success

    • Wesley,

      Is there any evidence to suggest that Narcan compromises resuscitative success

      There is no clear evidence of harm that I know of.

      It could be that they got to the point of termination and wanted to try anything before pronouncing him dead.

      It could be that medical command insisted that naloxone given before pronouncing the patient dead, because doctors may not be any more familiar with evidence.

      Nobody wants to admit that we cannot save young people from sudden cardiac arrest, so we tend to prolong resuscitation efforts and try things just to be able to state that we tried everything.

      The naloxone probably was not given until after it was clear that the resuscitation would not be successful, but even the most likely harm (if given earlier) would be to distract EMS from things that might work.


  9. I am not a medical expert. I am just a mother who lost her son a few days ago and am trying to figure out why. This past Thursday, May 24th 2018. My 24 year old son and some of his friends were partying/few drinks and smoking Shatter – a concentrated form of marijuana which was purchased at a dispensary. My son, who lived provinces away from me assured me many times during conversations that he did nothing else but drink and smoke this shatter. He was found slumped at his computer desk around 2pm Friday the 25th. He was not into opiates and I believe him when he said that he only smoked his shatter. When the roommates found him, they panicked and ran to get some Narcan and administered it to my son with no effect…they performed CPR they say but could not bring him around. Paramedics arrived, administered another round of Narcan to my son and also performed CPR all with no effect. My son was pronounced dead. The coroner contacted me and the verbal synopsis of her report was that my son had an enlarged heart and heart disease. My question is this… If someone has heart disease and or is experiencing a heart attach and is administered Narcan, can the Narcan cause them more harm? In other words can administering Narcan to someone undergoing cardiac arrest kill them. I notice many warnings that say to “tell your doctor if you have heart problems before using Narcan” , but none of those warnings state WHY. My sons toxicology won’t be back for several months. I’m upset that his roommates knew that he did not use opiates and still gave him Narcan (they although were not aware of his heart condition, no one was) , the paramedics jumped to the conclusion that my son was an opiate user and also administered Narcan. I want to know why do all the sights say the same thing, which is to “Tell your doctor if you have a history of heart disease before using narcan”, if it has no adverse effect on someone with heart condition? My son was only 24, and yes I found out from the coroner that he had heart disease. If Narcan has no adverse effects on people with heart conditions, then why are there all these warnings to “tell your doctor if you have heart problems.”? Would he have had a better chance at surviving had he not been given the Narcan… twice.?

    • My condolences on the death of your son.

      Administration of naloxone can be followed by acute pulmonary edema (heart failure), but this is rare.

      One of the reasons for this may be that the person’s pain was well managed by the opioids the person was taking and the increase in pain puts too much stress on a weak heart, producing the acute exacerbation of heart failure.

      The administration of naloxone should be slow and only to someone who has a pulse.

      Naloxone is not effective in cardiac arrest.

      The American Heart Association specifically states that naloxone should not be given during cardiac arrest.

      Wasting time giving an ineffective medication, rather than performing chest compressions, is more harmful than the rare side effects of naloxone.


  10. I was given narcan after telling the medics I only smoked half a marijuana cigarette days before. The medic told me I was on something! After receiving it my mouth got dry and I felt like I was dieing! I have been having a racing heart from 100 BPM to 170 within a minute just to stand, palitations and severe heart and chest pains ever since and getting worse 9 months later! I believe my problem was from hypoglycemia and dehydration. I’m terrified of EMS for not believing me and causing this! They should be sued!!!

    • You can always sue. Whether you can win a law suit is much more complicated.

      Your local EMS may be granted immunity from law suits, so your suit may be immediately thrown out.

      EMS will probably claim that you were not able to consent to treatment, or able to refuse treatment, or might claim that agreeing to anything means agreeing to everything, so they can do whatever they want to you. That is nonsense, but there are plenty of people in EMS who think that way.

      Naloxone (Narcan) is unlikely to produce any of the symptoms you describe unless you were very anxious or you were taking some medication that contains opioid medication. Some examples are cough syrup and anti-diarrhea medication.

      The psychological reaction to being forcibly injected with something (or having it forcibly squirted up your nose, if that is the route used) is a stress response – rapid heart rate, sweating, rapid respirations, discomfort, . . . . This is not the response to appropriate administration of naloxone.

      Did EMS measure your blood sugar? Did you suspect hypoglycemia at the time? Are you diabetic? Why do you suspect hypoglycemia and/or dehydration?

      You would also need to get their records of treatment, which should include several sets of vital signs, and a description of the observations they used to justify their treatment. The vital signs EMS documented after treatment with naloxone should support your description of the events.

      The problem is that the EMS documents may state that you were not capable of giving consent, due to disorientation, unconsciousness, or something else. You need to show that, if present, these statements are not true. You need to show that you did have the capacity to make informed decisions for yourself and either were not provided with the information to make an informed consent/refusal decision or that they ignored your informed refusal.

      You also want to know what their protocol specifically states as criteria for treatment with naloxone. You need the protocol that was current at the time you were treated. If the protocol has been changed, since then, you also want copies of every change, since any changes will probably be to protect patients from inappropriate treatment with naloxone by EMS. If the protocol is written by a competent EMS physician, it should limit indications for use of naloxone to decreased level of consciousness and inadequate respiratory drive and a reasonable suspicion of some opioid ingestion, or similar wording.

      If a patient’s breathing is adequate, there is no benefit to the patient from naloxone.

      If there is no reason to expected any kind of benefit to the patient, EMS is not providing medical care.

      If there is no reason to expected any kind of benefit to the patient, a doctor is also not providing medical care.


      • I suspected hypoglycemia because I have had a life long problem with it. I read that if uncontrolled it could cause delirium which was my issue. After I got to the hospital I passed a handful of clots as big as nightcrawlers and my urine was very bloody. I was in the hospital laying 3 days. After I got home and stood up a few minutes is when the problems began. I don’t know what happened to sick to investigate but I never had these problems before!! They have no right to assume anything! They didn’t ask me if I had problems with hypoglycemia just told me I was on something. I was anxious during the time. Why don’t they ask questions instead of assume and give especially because it wasn’t a life threatening situation ! I’m sure they will cover their butts! Just like the hospital! They knocked me out without permission immediately and I wasn’t hostile. I assume it could been anything I was given because EKG and Echo shows no heart problems just hypertension! Thank you for your advice! I believe it is a dangerous drug and shouldn’t be in the hands of anyone but a qualified professionals! Thank you for your hard work and caring enough about lives to spread the word!!!!!!!! The truth always comes out! God bless you!!!!!!!


        • They have no right to assume anything!

          Many assumptions are required to be made in the treatment of patients. We are expected to try to minimize the assumptions that are made, but we cannot eliminate them completely.

          They didn’t ask me if I had problems with hypoglycemia just told me I was on something. I was anxious during the time.

          It seems as if they do not know what they are doing, since anxiety and respiratory depression secondary to opioid overdose are not expected to accompany each other.

          Why don’t they ask questions instead of assume and give especially because it wasn’t a life threatening situation !

          Why do you assume that they should have known this was not a life threatening situation? You describe observations that should be treated as potentially life threatening.

          Delirium is life threatening, until ruled out. Treating delirium with naloxone is dangerous, because if the person is taking opioid medication, the resultant increase in stress may harm, or even kill, the patient.

          Just like the hospital! They knocked me out without permission immediately and I wasn’t hostile.

          Delirium, if the patient is agitated, is most appropriately treated by sedation. If a patient is not sedated, much more serious medical conditions can be caused by the delirium, including permanent disability, or death.

          Here is a link to one, of many, posts I wrote about the topic:

          Excited Delirium Strikes without Warning – Part I

          Based on the additional information you provided, it does not seem as if naloxone would have caused, or worsened, the medical conditions you describe. It does seem that it was inappropriate and irresponsible to give you naloxone.

          I hope that you are able to make a full recovery.


  11. Look I simply don’t believe that Narcan doesn’t have severe side effects. I was taken to he hospital for having a really low blood pressure as well as passing out. When I got there I explained what was going on and went over ALL medications that I was taking and that I wasn’t on any opiates at all. But because my blood pressure was so low and I was having issues that go along with that the quack told the nurse to give me some Narcan in my IV because he thought I was on something. I wasn’t and he didn’t even wait for a piss test or blood work. As the nurse was shooting it in my IV when it hit my system I felt like my heart was going to explode and I made her stop. I have never felt that much pain in my chest. Come to find out that that really low blood pressure wasn’t from opiates it was heart failure. I was sent to another hospital that is our trauma hospital in the area. So in reading these posts and others there should be more testing on this drug before anyone should be able to say that it doesn’t cause more damage or cause damage to the heart. More people should step up and speak out about it there is an issue!


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