# Methylnaltrexone

Source: https://onco.cc/drugs/methylnaltrexone/  
OnCo record `methylnaltrexone` (Treatment). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Methylnaltrexone (Relistor) is an injection or tablet that relieves the severe constipation caused by strong painkillers in people with advanced cancer, without blocking the pain relief itself.

## Summary

Methylnaltrexone was approved by the FDA in April 2008 for opioid-induced constipation in adults with advanced illness receiving palliative care when laxatives have failed, on two randomised placebo-controlled trials in hospice and palliative populations in which about half of patients had a bowel movement within four hours of the first subcutaneous dose versus around 15% on placebo; indications for chronic non-cancer pain and oral tablets followed in 2014 to 2016. The EU authorised Relistor in 2008. It is a standard second-line option in palliative care guidelines after conventional laxatives; naloxegol and naldemedine are oral alternatives. Abdominal pain, flatulence and nausea are common, and gastrointestinal perforation has been reported in patients with structural bowel disease. Marketed by Salix (Bausch Health).

## Fields

- Kind: Treatment
- Status: approved
- Last checked: 2026-09-24
- Tags: nci-list; supportive
- Brand: Relistor
- Modality: Peripherally acting mu-opioid receptor antagonist
- Mechanism: Quaternary derivative of naltrexone that does not cross the blood-brain barrier; blocks mu-opioid receptors in the gut to reverse opioid-induced constipation without reducing analgesia or precipitating withdrawal.
- Approvals: US 2008: Opioid-induced constipation in advanced illness receiving palliative care (chronic non-cancer pain and oral tablets added 2014 to 2016); EU 2008: Opioid-induced constipation in advanced illness receiving palliative care when laxatives are insufficient (Relistor)

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Methylnaltrexone
- MNTX 302 (NEJM 2008): https://doi.org/10.1056/NEJMoa0707377
- US label (DailyMed): https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=c488fb7c-0a5b-487c-b452-996809d1cb99
- NCI drug page: https://www.cancer.gov/about-cancer/treatment/drugs/methylnaltrexonebromide
- EPAR: https://www.ema.europa.eu/en/medicines/human/EPAR/relistor

## Connected records

- technologies: [Cancer pain management](https://onco.cc/technologies/pain-management/), [Early integrated palliative care](https://onco.cc/technologies/palliative-care/)
- targets: [Mu-opioid receptor](https://onco.cc/targets/oprm1/)
- companies: [Bausch Health](https://onco.cc/companies/bausch-health/)
- trials: [MNTX 302](https://onco.cc/trials/mntx-302/)
- key papers: [Methylnaltrexone for opioid-induced constipation in advanced illness (MNTX 302)](https://onco.cc/key-papers/paper-mntx-302-thomas-nejm-2008/)
- drugs: [Fentanyl (transmucosal, for breakthrough cancer pain)](https://onco.cc/drugs/fentanyl/)

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