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Naltrexone tablets


Naltrexone will help you to remain free from your dependence on opiate drugs.

It will be prescribed for you by a specialist clinic.

Keep your regular appointments with your doctor. This is so your progress can be checked.

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About naltrexone

Type of medicine

An opioid antagonist

Used for

To help prevent relapse in people with previous opioid or alcohol dependence

Also called


Available as


You will have been prescribed naltrexone if you have been through an opiate or alcohol detoxification regime and you are committed to remaining drug/alcohol-free. Alongside other forms of treatment and abstinence support, taking naltrexone can help you to remain free from your dependence.

Naltrexone acts by blocking opioid receptors in your brain and nervous system. This means that you will no longer experience the euphoria-like effects that you previously experienced from substance use. Knowing this will help to support your decisions to stay drug/alcohol-free.

Your treatment with naltrexone will be started and supervised by an appropriate specialist.

Before taking naltrexone

Some medicines are not suitable for people with certain conditions, and sometimes a medicine may only be used if extra care is taken. For these reasons, before you start taking naltrexone it is important that your doctor knows:

  • If you have taken any opiate drug in the previous 10 days. This includes any cough medicines or painkillers that contain opiates.

  • If you have any problems with the way your liver works, or if you have any problems with the way your kidneys work.

  • If you are pregnant or breastfeeding.

  • If you are taking or using any other medicines. This includes any medicines you are taking which are available to buy without a prescription, as well as herbal and complementary medicines.

  • If you have ever had an allergic reaction to a medicine.

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How to take naltrexone

  • Before you start the treatment, read the manufacturer's printed information leaflet from inside the pack. It will give you more information about naltrexone and will provide you with a full list of the side-effects which you may experience from taking it.

  • Take naltrexone exactly as your doctor tells you to. Your dose will be printed on the label of the pack to remind you about what was said to you.

  • When starting the treatment, your doctor will give you a small dose of 25 mg a day (half a tablet) and then will increase the dose to one 50 mg tablet a day. The usual maintenance dose is 50 mg (one tablet) each day, although your doctor may suggest that you take naltrexone on three days of the week only (such as two tablets on Mondays and Wednesdays and three tablets on Fridays).

  • Try to take your doses at the same time of day each day, as this will help you to remember to take the tablets regularly. Swallow the tablet with a drink of water. It can be taken either before or after a meal.

  • If you forget to take a dose at your usual time, take it when you remember. If you do not remember until the following day, leave out the forgotten dose but make sure that you remember to take that day's dose. Do not take two doses together to make up for a forgotten dose.

Getting the most from your treatment

  • Keep your regular appointments with your doctor and programme supervisor. This is so that your progress can be checked. Before you are prescribed naltrexone, your doctor is likely to test you to make sure that you are free from opiates. Also, your doctor will want to take a blood sample from you both before and during your treatment with naltrexone to check that your liver is working well.

  • Keep taking the tablets until your doctor tells you otherwise. You may need to continue to take naltrexone for a number of months, although your doctor will review this regularly.

  • If you are having any medical treatment, you must tell the person carrying out the treatment that you are taking naltrexone. This is particularly important to ensure that you get proper pain treatment in case of an emergency.

  • If you buy any medicines 'over the counter', always check with a pharmacist that they are suitable for you to take with naltrexone. Some medicines for cold and flu symptoms contain weak opioids, as do some medicines for diarrhoea - you must not take these.

  • These tablets are for you - do not give them to any one else, even if their condition appears to be the same as yours. If they are taken by anyone who is dependent on opioids, they could cause serious life-threatening withdrawal symptoms.

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Can naltrexone cause problems?

Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. The table below contains some of the most common ones associated with naltrexone. You will find a full list in the manufacturer's information leaflet supplied with your tablets. The unwanted effects often improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following continue or become troublesome.

Very common naltrexone side-effects (these affect more than 1 in 10 people)

What can I do if I experience this?

Headaches, muscle aches and pains

Ask your clinic to recommend a suitable painkiller

Feeling nervous or restless, lack of energy, difficulties sleeping

If any of these become troublesome, speak with your doctor for advice

Feeling sick (nausea), tummy (abdominal) discomfort

Stick to simple meals - avoid rich and spicy food

Common naltrexone side-effects (these affect fewer than 1 in 10 people)


Drink plenty of water to replace the lost fluids


Try to eat a well-balanced diet and drink plenty of water each day

Feeling dizzy

If this happens, do not drive and do not use tools or machines

Feeling thirsty, feeling shivery, lack of appetite, watery eyes, skin rash, erectile difficulties, difficulties passing urine, and mood changes

If any of these become troublesome, speak with your doctor for advice

If you experience any other symptoms which you think may be due to the tablets, please speak with your doctor or pharmacist for further advice.

How to store naltrexone

  • Keep all medicines out of the reach and sight of children.

  • Store in a cool, dry place, away from direct heat and light.

Important information about all medicines

Important information about all medicines

Never take more than the prescribed dose. If you suspect that you or someone else might have taken an overdose of this medicine, go to the accident and emergency department of your local hospital. Take the container with you, even if it is empty.

This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.

Do not keep out-of-date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.

If you have any questions about this medicine ask your pharmacist.

Report side effects to a medicine or vaccine

If you experience side effects, you can report them online through the Yellow Card website.

Further reading and references

Article history

The information on this page is written and peer reviewed by qualified clinicians.

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