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Methylnaltrexone Side Effects

In Summary

Commonly reported side effects of methylnaltrexone 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:

In addition to its needed effects, some unwanted effects may be caused by methylnaltrexone. In the event that any of these side effects do occur, they may require medical attention.

Major Side Effects

You should check with your doctor immediately if any of these side effects occur when taking methylnaltrexone:

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

Minor Side Effects

Some of the side effects that can occur with methylnaltrexone may not need medical attention. As your body adjusts to the medicine during treatment these side effects may go away. Your health care professional may also be able to tell you about ways to reduce or prevent some of these side effects. If any of the following side effects continue, are bothersome or if you have any questions about them, check with your health care professional:

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

Gastrointestinal

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]

Dermatologic

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

Other

Common (1% to 10%): Chills
Postmarketing reports: Malaise, pain, cases of opioid withdrawal[Ref]

Cardiovascular

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]

General

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

Local

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

References

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.

Not all side effects for methylnaltrexone may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

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