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Relistor Side Effects

Generic name: methylnaltrexone

Medically reviewed by Last updated on Apr 5, 2024.

Note: This document contains side effect information about methylnaltrexone. Some dosage forms listed on this page may not apply to the brand name Relistor.

Applies to methylnaltrexone: oral tablet. Other dosage forms:

Serious side effects of Relistor

Along with its needed effects, methylnaltrexone (the active ingredient contained in Relistor) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking methylnaltrexone:

Incidence not known

Other side effects of Relistor

Some side effects of methylnaltrexone may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Less common

For Healthcare Professionals

Applies to methylnaltrexone: oral tablet, subcutaneous kit, subcutaneous solution.


Very common (10% or more): Abdominal pain (up to 29%), flatulence (up to 13%), nausea (up to 12%)

Common (1% to 10%): Diarrhea,

Postmarketing reports: Perforation, cramping, vomiting[Ref]

Nervous system

Common (1% to 10%): Dizziness, tremor[Ref]


Common (1% to 10%): Hyperhidrosis, flushing[Ref]


Common (1% to 10%): Chills

Postmarketing reports: Malaise, pain, cases of opioid withdrawal[Ref]


Frequency not reported: Myocardial infarctions[Ref]

In an open-label, uncontrolled study (n=1034), 4 myocardial infarctions (1 fatal), 1 stroke (fatal), 1 fatal cardiac arrest, and 1 sudden death were reported. It is not possible to establish a relationship between these events and use of this drug.[Ref]


The most common adverse reactions included abdominal pain, nausea, diarrhea, hyperhidrosis, hot flush, tremor, and chills.[Ref]


Common (1% to 10%): Injection site reactions including stinging, burning, pain, redness, and edema[Ref]

Frequently asked questions


1. Cerner Multum, Inc. "UK Summary of Product Characteristics."

2. Cerner Multum, Inc. "Australian Product Information."

3. (2008) "Product Information. Relistor (methylnaltrexone)." Wyeth Laboratories

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.