Vol 16 Edition 3

Naloxone – the essential guide

What is naloxone?

Naloxone is a medicine that temporarily reverses the effects of opioids like morphine, codeine and heroin. Opioids depress the respiratory system, so overdosing on them is very dangerous. Administering naloxone can restore the breathing of someone who has overdosed, potentially saving their life.

What dose?

The amount of naloxone that needs to be administered in the event of an overdose varies depending on several factors, such as the person’s health, weight, the type of opioid they have taken and how much they have taken.

Generally, 400 micrograms (mcg) is considered a single dose of naloxone when it is injected. Most injectable naloxone comes in doses of 400mcg or multiples of this: ampoules contain 400mcg and each marker on the barrel of a Prenoxad unit is a 400mcg dose.

Most guidelines for administering injectable naloxone recommend a single 400mcg dose with additional doses to be administered if the person remains unresponsive.

Paramedics tend to administer larger doses of naloxone. This can be done safely because naloxone does not have any intoxicating or harmful effects. Paramedics do this because they need to act quickly to save a person’s life. Most of the time they will not know what opioid(s) the person has taken. For strong synthetic opioids like fentanyl, more naloxone will be needed to restore a person’s breathing.

Micrograms and milligrams

They might sound similar, but 1 milligram is the same as 1000 micrograms. So, 400 micrograms (a single dose of IM/IV naloxone) is the same as 0.4 milligrams. Intranasal naloxone, which has a different method of being absorbed into the bloodstream, requires larger doses to be effective. This is why a single dose of IN naloxone is higher (Nyxoid is 1.8mg).

Which route of administration?  

Intravenous (IV) or injected into a vein. Naloxone can be administered intravenously. However, because intravenous injections are difficult and require training, IV administration is generally only performed by medical professionals in medical settings.

Intramuscular (IM) or injected into a muscle. Naloxone can be injected into a muscle – usually the thigh or upper arm. This is the most common way naloxone is administered. 400 micrograms of IM naloxone is generally considered a single dose of naloxone administered intramuscularly.

Intranasal (IN) or sprayed into the nose. Naloxone can be delivered via a nasal spray. IN naloxone has only recently become available in Australia but has been available in the US and Canada for several years. Because IN naloxone is absorbed more slowly through mucus membranes, the amount of naloxone considered a single dose is much larger. The time it takes for the medicine to take effect can also be longer. The only kind of intranasal naloxone available in Australia comes in a 1.8 milligram single dose.

Intraosseous (IO) infusion is the process of injecting directly into the marrow of a bone. This provides a non-collapsible entry point into the systemic venous system. This technique is used to provide fluids and medication when intravenous access is not available or not feasible.

Types of naloxone

Ampoules – these are small glass vials that contain 400 micrograms of naloxone in 1 millilitre of water – Used for IM/IV administration. The naloxone must be ‘drawn up’ from the ampoule using a needle and syringe to administer it with an injection.

Prenoxad – this is a pre-filled syringe that contains 2 milligrams (five single doses) of IM/IV naloxone. Naloxone should be administered a single dose at a time (each dose is marked with a black line on the syringe’s barrel). Follow the guidelines about additional doses.

Nyxoid – this is the only type of intranasal naloxone available in Australia. Each pack comes with two single dose units of naloxone (containing 1.8 mg each). Because it is intranasal, no needles are needed to administer it. When using Nyxoid, you can only administer a full dose.

– James Petty

Naloxone and adults – what do the ambulance services do?

Naloxone and adults – what do the ambulance services do?

Ambulance Victoria

Heroin overdose: naloxone 1.6-2mg IM

Other opioid overdose: naloxone 100mcg IV (repeat 100mcg every 2 minutes – max 2mg)

From their guidance:

  • Patients who are managed using the ‘Other opioid overdose’ protocol should receive supportive care, transport to hospital and titrated doses of naloxone to target the return of adequate ventilation.
  • Synthetic opioids, especially fentanyl analogues are increasingly used recreationally. These may require higher doses of naloxone than usual to reverse their effects.

Source: https://www.ambulance.vic.gov.au/wp-content/uploads/2019/03/Clinical-Practice-Guidelines-2018-Edition-1.8.pdf and Ambulance Victoria

Queensland Ambulance Service

1.6mg single dose IM

In special circumstances (Critical Care Paramedic) incremental 50mcg IV doses can be administered.

Source: https://www.ambulance.qld.gov.au/docs/clinical/dtprotocols/DTP_Naloxone.pdf and Queensland Ambulance Service

New South Wales Ambulance

Suspected narcotic overdose:

  • 800mcg (2mL) IM/IV undiluted bolus Repeat 400mcg (1mL) bolus every 2 minutes. Maximum dose: 2mg (5mL)

Opioid overdose:

  • 100mcg (1mL) IV diluted bolus. Repeat every 2 minutes until adequate clinical response
  • 100mcg (1mL) IM diluted bolus. Repeat every 5 minutes until adequate clinical response

Source: http://www.ambo.com.au/download/protocol_2011.pdf

ACT Ambulance Service

1st dose: 0.8mg IM

2nd dose: 0.8mg IM

OR 2nd and subsequent doses: 0.4mg IV increments, fast push. May repeat IV dose up to 3 times (to maximum of 2mg). (All doses may be administered IM or IV as the situation demands).

Source: http://cdn.esa.act.gov.au/wp-content/uploads/NALOXONE-Jan-2014.pdf and ACT Ambulance Service

Ambulance Tasmania

1st dose: 0.8mg IM

After five minutes and inadequate response: 2nd dose: 0.8mg IM or IV followed by 400mcg IM or IV to a total of 2mg.

There is also the option of giving small doses to reverse respiratory depression and keep the patient safe. This is classified in the Ambulance Tasmania Clinical Practice Guidelines as partial reversion and is 100 mcg increments titrated as required.  This is becoming a popular alternative in treatment, but the choice is left up to the paramedics at the time.

Source: https://www.dhhs.tas.gov.au/__data/assets/pdf_file/0018/107334/A00_-_Ambulance_Tasmania_Clinical_Practice_Guidelines_for_Paramedics_and….pdf

and Ambulance Tasmania

SA Ambulance Service

SA Ambulance Service has different clinical practice protocols for Intensive Care Paramedics (ICPs) and for Paramedics regarding suspected narcotic overdose and naloxone dosage.

The Guideline for ICPs for suspected narcotic overdoses:

  • For adults, naloxone doses are titrated to restore spontaneous ventilation. Select from:
    • IV: 100 microgram aliquots, every 30-60 seconds
    • Intranasal: 120 microgram aliquots, every 30-60 seconds
    • IM: 400 microgram aliquots, every 1-2 minutes

The Guideline for Paramedics for suspected narcotic overdoses:

  • In adults consider:
    • Naloxone 100 micrograms IV PRN or;
    • Naloxone 120 micrograms IN PRN or;
    • Naloxone 400 micrograms IM PRN

Source: SA Ambulance Service spokesperson

St John Ambulance Western Australia


  • Dilute 0.4mg (400mcg) /1ml with 9mls NaCL for IV/IO administration
  • IM: 0.4mg (400mcg) every 5 minutes as needed up to 10mg
  • IV/IO: Administer up to 400mcg titrated to effect. Repeat every 2 minutes as clinically required to a maximum of 10mg.

Source: St John Ambulance Western Australia

St John Ambulance Northern Territory

  • 800mcg IM. Repeat at 10 min PRN.  Total max dose 4mg.
  • 100mcg IV/IO. Repeat at 5 min PRN. No max dose.

Source: St John Ambulance Northern Territory