Naltrexone

How is naltrexone used?

Naltrexone is taken as a tablet and usually taken daily. The length of the course will depend on each person’s needs and situation.⁶

Naltrexone can also be administered via an implant, an unregistered form of naltrexone treatment which is yet to be supported by high-quality evidence. It can be accessed in Australia under the TGA Special Access Scheme.

Naltrexone for alcohol or opioid dependence

To be eligible for naltrexone treatment, a person must:

• not be currently using any opioids* or require opiate-based pain relief
• have no existing liver conditions, such as acute hepatitis (liver function tests may be required before and during naltrexone treatment)
• seek advice if you are pregnant or breastfeeding.^{4, 7}

* If using naltrexone for opioid dependence a person typically needs to be free of opioids for 7–10 days before starting naltrexone treatment; otherwise they may experience instant withdrawal. Sometimes people are tested to confirm they are no longer using opioid drugs before beginning treatment. An example is the Naloxone Challenge Test (NCT), where naloxone is administered to understand a person’s current level of physical dependence on opioids.³

How effective is it?

Naltrexone may not work for everyone, so it’s important to consult a doctor or alcohol and other drug (AOD) counsellor to find the best approach.

Generally, naltrexone treatment is more likely to be effective if a person has good social support and they are highly motivated to change.^{8, 9}

When treating alcohol dependence, naltrexone may work better at reducing heavy drinking and overall alcohol use than at helping people stay completely alcohol-free.¹⁰

Effects of naltrexone

The use of any drug can have risks. It’s important to be careful when taking any type of drug.

Naltrexone can affect everyone differently, based on:

• size, weight and health
• whether the person is used to taking it
• whether other drugs are taken around the same time
• the amount taken.

Onset and duration of effects

How fast a drug takes effect and how long it lasts can vary depending on how it's taken.

Naltrexone is usually taken daily as an oral tablet, but it can also be injected monthly in an extended-release form.^{6, 11}

Side effects

Naltrexone has few side effects, and they are usually mild. Side effects may be reduced by taking naltrexone with food and often go away once your body gets used to the medication.¹²

Common side effects include:

• nausea
• headache
• dizziness
• drowsiness
• stomach pain
• reduced appetite
• nervousness
• restlessness
• sweating.^{13, 14}

Less common side effects include:

• feeling energetic
• thirst
• diarrhoea, constipation
• skin rashes
• delayed ejaculation
• irritability
• chills.¹⁴

Overdose

Naltrexone lowers a person’s tolerance to opioids. This means there is a serious risk of overdose if a person uses an opioid during or after naltrexone treatment finishes.¹⁵

If opioids have been taken during or immediately after naltrexone treatment, call triple zero (000) and request an ambulance if you or someone else has any of the following symptoms (emergency services are there to help and can provide instructions over the phone):

Signs of opioid overdose can include:

• unconscious or non-responsive
• slow breathing, abnormal breathing, or not breathing at all
• slow or no heartbeat and pulse
• choking or gurgling sounds
• skin colour changes, especially lips and fingernails
• bluish-purple skin for people with lighter complexions
• greyish or ashen skin for people with darker complexions
• vomiting
• cool or clammy (wet and sweaty) skin
• small ‘pinpoint’ pupils.^{16, 17}

Learn more on overdose and drug-related emergencies

Naloxone

Naloxone (also known as Nyxoid®/Narcan®) temporarily reverses the effects of opioid overdose. It’s available for free over the counter from most local pharmacies and can be administered by anyone, including family or friends and bystanders.¹⁸

If a person does not respond to the first dose after 3 minutes, give them a second dose. This can be repeated until the ambulance arrives.^{19, 20}

Find naloxone near you

Mixing naltrexone with alcohol and other drugs

Mixing naltrexone with other drugs can have unpredictable effects and increase the risk of harm.

Mixing includes using more than one drug (including alcohol or medications) at the same time, or one after another. You should also consider what drugs you’ve taken in the last 24 hours.

• Naltrexone and alcohol: if a person drinks alcohol while using naltrexone, they will still experience the impairment effects of alcohol. Their judgement, coordination and ability to do things like drive a car or operate machinery will still be affected.⁷
• Naltrexone and opioids (codeine, heroin, oxycodone): naltrexone lowers a person’s tolerance to opioids, and makes an overdose more likely if opioids like heroin are used after missing a naltrexone dose or stopping treatment.

If you are taking naltrexone:  

• Inform medical staff if you are likely to be given opioid painkillers (such as codeine or oxycodone) so they can care for you properly.
• Always start with a small amount if you plan to use heroin, oxycodone, or other opioids, to prevent the risk of overdose and keep naloxone nearby.^{14, 21}

Using more than one drug or type of drug at the same time is called polydrug use.¹⁷

Reducing harm

There are ways you can reduce the risk of harm when taking naltrexone:

• Follow your doctors’ instructions on how and when to take naltrexone. Do not stop taking naltrexone or change the dose without talking to your doctor.
• Naltrexone may affect your alertness and/or coordination.  Avoid driving or using machinery if you feel affected.
• Do not use naltrexone if you have used opioids within 7-10 days.
• Do not use naltrexone if you have liver disease or liver failure.
• If you experience any side effects or discomfort, talk to your doctor to make sure that naltrexone is right for you.
• Naltrexone has the potential to interact with several drugs and medications.  Talk with your doctor about the other drugs and medications you use.
• Tell your doctor if you are pregnant or breastfeeding, or plan on becoming pregnant, while taking naltrexone.¹⁴

Coming down

Naltrexone is not known to cause comedown effects

Long-term effects

There is limited information on the long-term effects of naltrexone.

People taking naltrexone pharmacotherapy usually take it for about 3 to 6 months, with some people needing treatment for up to 12 months.⁶

Naltrexone and mental health

One of the main uses for naltrexone is the treatment of alcohol dependence. It’s also sometimes used for opioid dependence.⁶

The relationship between naltrexone, alcohol, and mental health is complex.

For example, some people may drink alcohol to cope with their mental health concerns. Although alcohol might feel like it relieves symptoms of anxiety or depression in the short term, it is more likely to lead to longer-term anxiety and depression.^{22, 23}

However, pharmacotherapies for alcohol, such as naltrexone, can improve physical and mental health by reducing alcohol intake, withdrawal symptoms, and cravings.^{4, 24, 25}

Pharmacotherapy provides greater life stability, supporting improved wellbeing, relationships, and social functioning.^{4, 26}

Tolerance

There is no evidence that naltrexone causes tolerance.

Dependence

There is no evidence of physical dependence for patients talking naltrexone pharmacotherapy.⁶

A person who enters a naltrexone pharmacotherapy program for alcohol or opioid dependence can rely on naltrexone to reduce the desirable effects of drugs. The program can help them stop or reduce their use of alcohol or opioids and, as a result, reduces their risk of related harms.²⁷

Withdrawal

Withdrawal refers to the symptoms that can occur when someone who is dependent on a drug, or who has been using it regularly over time, stops or reduces their use.²⁸

Withdrawal can include physical symptoms (such as headaches, or nausea) and psychological symptoms (such as anxiety, or depressed mood).²⁸

Symptoms - including how strong they are and how long they last - will vary depending on the type of drug and a person’s history of use.²⁸

There are no known naltrexone withdrawal symptoms, however if you experience symptoms after stopping use, or have concerns, contact your doctor or the help and support services listed below for advice and support.⁶

Social and emotional support should continue after pharmacotherapy ends to prevent a return to previous levels of alcohol use.⁶

Precipitated withdrawal

If a person is currently dependent on opioids, or regularly takes opioid medications, they can experience sudden withdrawal symptoms when they are given naltrexone.²⁹

While these symptoms can be very unpleasant, they should go away as the naltrexone wears off.

Reduced tolerance and overdose risk

Naltrexone can be used in treatment for opioid dependence.⁴

After withdrawing from opioids, your body is no longer used to it and your tolerance drops. This means if you use the same amount as before, it can be too much for your body and cause an overdose. Always start with a lower dose after a break from opioids.³⁰

Pregnancy and breastfeeding

There haven’t been many large studies on naltrexone use and pregnancy, meaning there’s not enough evidence to know the safety of naltrexone during pregnancy.³¹

Naltrexone can pass to the unborn baby via the placenta. Some studies in animals have found an increased risk of harm to the developing baby. However, no long-term effects on babies have been observed in people who have taken naltrexone during pregnancy.^{31, 32}

Naltrexone can also pass to the baby through breastmilk. But this doesn’t appear to cause any harmful effects for the baby or pregnant person.³²

One potential benefit of naltrexone compared with other opioid pharmacotherapies is a lower risk of neonatal opioid withdrawal syndrome in the baby. But, more studies are needed to prove this.^{11, 33}

The potential benefits and risks of naltrexone should be considered for each person individually. If you’re pregnant or trying to become pregnant, talk to your doctor about using naltrexone for alcohol or opioid dependence treatment.³¹

Getting Help

If your use of alcohol or other drugs is affecting your health, family, relationships, work, school, financial or other life situations, or you’re concerned about someone, there is help and support.

• Call the National Alcohol and Other Drug Hotline on 1800 250 015 for free and confidential advice, information and counselling about alcohol and other drugs.
• Search our Help and Support directory to find your preferred support, by adding your location or postcode and filtering by service type.