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Home > Medicines & Drugs > Naltrexone

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Naltrexone

  • Naltrexone can only be used to help those who have not taken opioid drugs for at least 7 - 10 days
  • Taking enough opioids to overcome the blocking effect of this medicine can cause an overdose
  • Keep your regular appointments with your doctor so your progress can be checked

About naltrexone

Type of medicineOpioid antagonist
Used forOpioid dependence including heroin, methadone or other similar opioid drugs of addiction
Also calledNalorex
Opizone
Available asTablets

Naltrexone is used in combination with other medicines to help those who are dependent on drugs such as heroin (opioids), overcome their addiction. Naltrexone acts by blocking receptors in the brain to block the action of opioids. Individuals will no longer experience the euphoria previously experienced after taking opioids.

Naltrexone can only be used to help those who have not taken opioid drugs for at least 7 - 10 days.

Before taking naltrexone

Before taking naltrexone make sure your doctor or pharmacist knows:

  • If you are pregnant, trying for a baby or breast-feeding
  • If you suffer from liver or kidney problems

How to take naltrexone

  • Take naltrexone exactly as directed by your doctor
  • Important: Taking enough opioids to overcome the blocking effect of this medicine can cause an overdose

Getting the most from your treatment

  • Keep your regular appointments with your doctor so your progress can be checked
  • Continue to take naltrexone for as long as your doctor advises
  • Your doctor may want to take a blood sample from you before and during your treatment with naltrexone, to check that your liver is working well

Can naltrexone cause problems

Along with their useful effects all medicines can cause unwanted side effects, which usually improve as your body adjusts to the new medicine. Speak with your doctor or pharmacist if any of the following side effects continue or become troublesome.

Side-effectsWhat can I do if I experience this
NauseaEat little and often. Stick to simple foods such as dry toast.
VomitingDrink plenty of liquid. Stick to simple foods such as dry toast.
DiarrhoeaDrink plenty of water to replace lost fluids.
ConstipationTry to eat a well balanced diet containing plenty of fibre and drink 6 - 8 glasses of water each day.
HeadachesAsk your pharmacist to recommend a suitable pain-killer. If headache continues speak with your doctor.
DizzinessMake sure your reactions are normal before driving, operating machinery or doing any other jobs which could be dangerous if you were not fully alert. Avoid alcohol - it will increase any feelings of dizziness.
Skin rashesAvoid scrubbing your skin. Use a soap substitute. Leave the affected area exposed to the air as much as possible.

Important: If you experience tummy pain lasting more than a few days, white bowel movements, dark urine or yellowing of the eyes, stop taking naltrexone and consult your doctor immediately.

Other side-effects may include difficulty sleeping, anxiety (worry), nervousness, tummy pain, lack of energy, joint and muscle pain, loss of appetite, increased thirst, increased energy, feeling down, tiredness, irritability, sexual problems, chills, chest pain, increased sweating, watery eyes and bruising. If you experience these or any other worrying symptoms, which you think may be due to this medicine, discuss them with your doctor or pharmacist.

How to store naltrexone

  • Keep all medicines out of the reach of children
  • Store in a cool, dry place, away from direct heat and light

Important information about all medicines


  • Keep all medicines out of the sight and reach of children.
  • Make sure that the person prescribing this medicine knows about any other medicines that you are taking. This includes medicines you buy and herbal and homeopathic medicines.
  • If you buy any medicines check with a pharmacist that they are safe to take with your other medicines.
  • Before taking this medicine tell your doctor if you have ever had an allergic reaction after taking any medicine.
  • Never take more than the prescribed dose. If you suspect that you or someone else has taken an overdose of this medicine go to the accident and emergency department of your local hospital at once. Always take the container with you, if possible, even if it is empty.
  • If you are having any treatment like an operation or dental treatment tell the person carrying out the treatment which medicines you are taking.
  • Always read the printed information leaflet that comes with your medicine.
  • This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.
  • Never 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.
Comprehensive patient resources are available at www.patient.co.uk
© EMIS 2008DocID:
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dils2375		Last Reviewed:
9 Aug 2007		Version:
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