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What does it do?

Naltrexone helps you abstain from alcohol or opioid drugs (e.g. morphine, oxycodone, heroin). It reduces alcohol cravings and the high you get when using opioids.

Before you start

  • Tell your doctor if you have used opioids in the last 10 days because this will cause severe withdrawal symptoms.
  • Tell your doctor if you have kidney problems.
  • Tell your doctor if you are pregnant, planning to become pregnant, or breastfeeding.

How should you take it?

Take naltrexone regularly as directed with a glass of water.

What if you forget a dose?

If it is nearly time for your next dose, skip the missed dose and take your next dose at the usual time. Otherwise, take the missed dose as soon as you remember. Do not take two doses at the same time.

Can you take other medicines?

Tell your pharmacist or doctor about all medicines or treatments that you may be taking, including vitamins, herbal products or recreational drugs.

What side effects might you notice?

These side effects are similar to withdrawal symptoms that you might get when coming off alcohol or opioids.

Side EffectsRecommended action


Tell your doctor

Nausea, vomiting

Headache, dizziness, trouble sleeping

Joint or muscle aches or pains

Tell your doctor if troublesome

If you notice any other effects, discuss them with your doctor or pharmacist.

Other information:

  • Do not use opioids while you are taking naltrexone. This can be life-threatening.
  • Do not stop taking naltrexone without talking to your doctor first.
  • After you have stopped taking naltrexone, you may be more sensitive to opioids and have a higher risk of overdose if you start using them again.

This leaflet contains important, but not all, information about this medicine.

Prepared by the MyMedicines Committee at Christchurch Hospital, Te Whatu Ora - Waitaha, New Zealand. June 2024

For more general information about this sheet and its contents, see: What does a My Medicines sheet cover?

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About My Medicines

My Medicines Patient Information Leaflets (PILs) contain important, but not all, information about the medicines they describe.

For more information about the sheets, see: What does a My Medicines sheet cover?

My Medicines is developed by a team at Te Whatu Ora – Waitaha. Our team is made up of doctors, pharmacists, and a non-medical person to help us keep to plain language. We also discuss our information with specialist health professionals or groups when needed