Also called methylnaltrexone

Key points about Relistor

  • Relistor is used to treat constipation caused by opioid pain medicines.
  • Relistor is also called methylnaltrexone.
  • Find out how to take it safely and possible side effects.
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Relistor is a medicine used to treat constipation that is caused by opioid pain medicines (examples include morphine, oxycodone, tramadol, codeine, dihydrocodeine, methadone, fentanyl and pethidine). Relistor is used when other medicines used to treat constipation (laxatives) haven't been effective.

Opioids can help relieve moderate to severe pain caused by cancer or advanced illness. Unfortunately, opioids often cause constipation which can be very uncomfortable and, if severe enough, can be harmful. Relistor helps to treat constipation by blocking the effects of opioids in the gastrointestinal tract, without affecting pain relief. Read more about opioids in palliative care

In Aotearoa New Zealand Relistor comes as an injection, which is given under the skin (subcutaneous injection).

  • The dose of Relistor will be different for different people, depending on your body weight.
  • Relistor is usually given on alternate days. The interval between doses may be longer. If there's been no bowel movement within 24 hours of the last dose, an additional dose may be given. 
  • No more than 1 dose of Relistor should be given in a 24-hour period. 
  • The pharmacy label on your medicine will tell you how much to use, how often to use it and any special instructions.

Your healthcare provider will show you how to use Relistor. The following is a guide.

Time of day

Relistor injection is usually given as a single dose on alternate days. You can use Relistor at any time of day, with or without food. 

Injection site

Relistor is given as an injection under your skin (subcutaneous injection) by a doctor or nurse. If you are injecting it yourself, your doctor or nurse will show you how to give it. Relistor may be injected into the upper arm, tummy area or thigh. Don't inject Relistor into a vein or muscle.  

Rotate the injection site to avoid repeated injections at the same spot. Don't inject into areas where the skin is tender, bruised, red or hard. Avoid areas with scars or stretch marks.

Ensure there is a toilet or bed pan close by following your injection

The medicine may start working within 30 minutes so it's important to be near a toilet, with assistance available if necessary, since bowel movement may happen very quickly.

Missed dose

If you miss a dose of Relistor, you should contact your doctor or pharmacist for advice. Don't take a double dose to make up for the dose you missed.

Here are some things to know when you're taking Relistor. Other things may be important as well, so ask your healthcare provider what you should know about.

  • Relistor may cause dizziness in some people. As a precaution, don't drive or use tools or machinery until you know how this medicine affects you.
  • Relistor can interact with other medicines. Tell your doctor or pharmacist about all medicines you are taking including over-the-counter medicines and herbal supplements or vitamins.
  • Remind any doctor, dentist, or pharmacist you visit that you are taking Relistor.
  • If you have a peptic ulcer or colostomy bag, let your doctor know. 
  • If you are pregnant or breastfeeding, let your doctor know

Like all medicines, Relistor can cause side effects, although not everyone gets them.

Side effects What should I do?
  • Tummy pain
  • Gas, bloating
  • Nausea (feeling sick) 
  • Dizziness
  • Excessive sweating
  • These are quite common when you first start using Relistor. 
  • Tell your doctor if these side effects bother you.
  • Don't drink alcohol, drive or operate machinery if this medicine makes you feel dizzy.
  • New, persistent or worsening
    abdominal pain, nausea, or
  • Abdominal cramping or abdominal pain are common, after using Relistor. However if this pain is not relieved by having a
    bowel motion, tell your doctor immediately or ring Healthline 0800 611 116.
Did you know that you can report a medicine side effect to CARM (Centre for Adverse Reactions Monitoring)? Report a side effect to a product.(external link)

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Credits: Sandra Ponen, Pharmacist, Healthify He Puna Waiora. Healthify is brought to you by Health Navigator Charitable Trust.

Reviewed by: Angela Lambie, Pharmacist, Auckland

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