Emergency & antidotes
Naloxone
Opioid-overdose reversal — Rapidly reverses opioid overdose — a safe, life-saving antidote increasingly carried in the community.
Education and reference only. This is a plain-language class overview — it deliberately contains no doses. Always check the current Summary of Product Characteristics (SmPC), the BNF and your local formulary before prescribing or administering any medicine.
Quick answer
What is Naloxone?
Naloxone is an emergency medicine that rapidly reverses the effects of an opioid overdose, particularly the slowed or stopped breathing that makes it deadly. It comes as an injection or nasal spray designed to be used quickly by anyone, including non-medical bystanders.
- How it works: Opioids cause overdose by occupying receptors in the brain that suppress breathing.
- In practice: In practice naloxone is the emergency antidote that reverses the dangerous breathing-suppression of an opioid overdose (heroin, methadone, oxycodone, morphine and similar), and the public-health shift has been to put it into the hands of people who might witness one — those who use opioids, their families and friends, hostels and outreach services — as easy-to-use injections or nasal sprays.
What it is
Naloxone is an emergency medicine that rapidly reverses the effects of an opioid overdose, particularly the slowed or stopped breathing that makes it deadly. It comes as an injection or nasal spray designed to be used quickly by anyone, including non-medical bystanders.
How it works
Opioids cause overdose by occupying receptors in the brain that suppress breathing. Naloxone has a stronger pull for those same receptors and knocks the opioid off them, instantly blocking its effect and restoring the drive to breathe. Because it only displaces opioids, it has no effect (and does no harm) if opioids are not involved.
In practice
In practice naloxone is the emergency antidote that reverses the dangerous breathing-suppression of an opioid overdose (heroin, methadone, oxycodone, morphine and similar), and the public-health shift has been to put it into the hands of people who might witness one — those who use opioids, their families and friends, hostels and outreach services — as easy-to-use injections or nasal sprays. The practical themes are: recognise the overdose (unresponsive, very slow or stopped breathing, pinpoint pupils, blue lips), call 999, give naloxone, and start rescue breaths/CPR as needed. A crucial counselling point is that naloxone wears off faster than many opioids, so the overdose can return as it fades — the person must always go to hospital and not be left alone, and repeat doses are often needed. It can trigger sudden, unpleasant opioid withdrawal (agitation, sweating, vomiting) in dependent people, which is uncomfortable but not life-threatening and is the trade-off for restoring breathing. It only works on opioids and does no harm if given to someone whose collapse turns out not to be opioid-related, so when in doubt it is given.
Examples
Practical use
How to take it & use it well
- Use it as soon as you suspect an opioid overdose, recognised by someone being unresponsive, breathing slowly or not at all, with pinpoint pupils and blue or grey lips.
- Call 999 first or as you give it, because naloxone buys time but the person still needs emergency medical care.
- Give it as you have been shown, either as a nasal spray or an injection into a muscle such as the thigh, following the simple steps in your kit.
- If there is no response after a short wait, give a further dose, as more than one is often needed to get someone breathing again.
- Stay with the person and, if you are trained, give rescue breaths or chest compressions while you wait for the ambulance.
- Never leave the person alone, because naloxone wears off faster than many opioids, so the overdose can return and they may stop breathing again.
Common uses
- Emergency reversal of opioid overdose
- Community/take-home kits for people at risk and their contacts
- Reversing opioid effects in healthcare settings
Monitoring
- Breathing and responsiveness, with repeat doses until help arrives
- Return of overdose as naloxone wears off (hospital assessment essential)
- That at-risk people and their contacts are supplied and trained
Weighing it up
Advantages & disadvantages
Advantages
- It can rapidly reverse the dangerous slowing of breathing caused by an opioid overdose.
- It is designed to be used by family, friends and bystanders with very little training.
- It only acts on opioids, so it is safe to give even if you are not sure what has been taken.
- It is available as an easy-to-use nasal spray as well as an injection.
- Having a kit to hand can save a life in the minutes before an ambulance arrives.
Disadvantages
- Its effect wears off faster than many opioids, so the overdose can return and repeat doses may be needed.
- It is a rescue treatment only and never removes the need to call 999 and go to hospital.
- In someone dependent on opioids it can bring on uncomfortable withdrawal, which is unpleasant but not life-threatening.
- It does nothing for an overdose that is not caused by opioids.
- It must be kept in date and to hand to be of any use in an emergency.
Key safety principles
What to watch for
- It wears off faster than many opioids — the overdose can return, so always call 999, give repeat doses if needed, and never leave the person alone.
- Recognise overdose (unresponsive, very slow/stopped breathing, pinpoint pupils, blue lips), give naloxone and do rescue breaths/CPR as needed.
- It can cause sudden opioid withdrawal in dependent people (uncomfortable, not life-threatening); it only works on opioids and is safe to give if unsure.
Key interactions
What to avoid or check alongside
- Because it wears off sooner than the opioid, breathing can slow again later, so the person must never be left alone and must still go to hospital.
- In people dependent on opioids it can trigger sudden withdrawal, with sweating, agitation and feeling sick, which is distressing but not dangerous.
- It only works against opioids and will not reverse overdoses from alcohol, sedatives or stimulants, though it is still safe to give if you are unsure.
- Check the expiry date and replace the kit when needed, and store it away from extremes of heat and cold so it works when required.
- Tell others who might need it where your kit is kept and how to use it, as you cannot use it on yourself once unconscious.
Patient & carer advice
- If you think someone has overdosed on opioids, call 999, give naloxone and start rescue breaths — it cannot harm them if you are wrong
- It can wear off before the drug does, so they must go to hospital and not be left alone
- Carry a kit if you or someone close uses opioids, and show family and friends how to use it
Answers
Naloxone: frequently asked questions
How do I know if someone has had an opioid overdose?
Signs include being unresponsive or impossible to wake, very slow or stopped breathing, pinpoint pupils and blue or grey lips and fingertips. If you see these after opioid use, treat it as an emergency: call 999, give naloxone if you have it, and start rescue breaths or CPR if you are trained.
Why might the overdose come back after naloxone works?
Naloxone wears off faster than many opioids, so once it fades the opioid can take over again and breathing can slow once more. This is why you must call 999, give repeat doses if needed, stay with the person, and get them to hospital even if they seem to recover.
Is it safe to give naloxone if I am not sure it is opioids?
Yes. Naloxone only acts on opioids and has no harmful effect if opioids are not involved, so it is safe to give when you are unsure. If in doubt and someone is not breathing properly, give it, call 999 and start rescue breaths or CPR.
Will naloxone make the person angry or unwell?
In someone dependent on opioids, naloxone can cause sudden withdrawal, with agitation, sweating, feeling sick and being upset. This is unpleasant but not life-threatening, and it is far better than the alternative. Stay calm, keep them safe and wait with them for the ambulance.
What should I do after giving naloxone?
Always call 999 and stay with the person, because the effect can wear off and the overdose can return. Keep them on their side if they are breathing, be ready to give another dose or rescue breaths, and let the ambulance crew take over. Never leave them alone.
Authoritative sources
Always verify against the source
This overview is for orientation. For doses, interactions, contra-indications and the full monograph, use:
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