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Relistor Side Effects

Generic Name: methylnaltrexone

Note: This page contains side effects data for the generic drug methylnaltrexone. It is possible that some of the dosage forms included below may not apply to the brand name Relistor.

In Summary

Common side effects of Relistor include: abdominal pain, nausea, and flatulence. See below for a comprehensive list of adverse effects.

For the Consumer

Applies to methylnaltrexone: oral tablet

Other dosage forms:

As well as its needed effects, methylnaltrexone (the active ingredient contained in Relistor) may cause unwanted side effects that require medical attention.

Major Side Effects

If any of the following side effects occur while taking methylnaltrexone, check with your doctor immediately:

Incidence not known:
  • Chills
  • diarrhea
  • fear or nervousness
  • increased sweating
  • severe abdominal or stomach pain
  • severe or persistent diarrhea
  • yawning

Minor Side Effects

Some methylnaltrexone side effects may not need any medical attention. As your body gets used to the medicine these side effects may disappear. Your health care professional may be able to help you prevent or reduce these side effects, but do check with them if any of the following side effects continue, or if you are concerned about them:

Less common:
  • Full or bloated feeling
  • headache
  • muscle spasms
  • pressure in the stomach
  • runny nose
  • swelling of abdominal or stomach area
  • vomiting

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]


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]

Frequency not reported: Myocardial infarctions[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]


1. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0

2. Cerner Multum, Inc. "Australian Product Information." O 0

3. "Product Information. Relistor (methylnaltrexone)." Wyeth Laboratories, Philadelphia, PA.

It is possible that some side effects of Relistor may not have been reported. These can be reported to the FDA here. Always consult a healthcare professional for medical advice.

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.