Methylnaltrexone Side Effects

Medically reviewed by Drugs.com. Last updated on Jul 25, 2024.

Applies to methylnaltrexone: oral tablet.

Other dosage forms:

• subcutaneous solution

Common side effects of methylnaltrexone

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 side effects

• full or bloated feeling
• headache
• muscle spasms
• pressure in the stomach
• runny nose
• swelling of the abdominal or stomach area
• vomiting

Serious side effects of methylnaltrexone

Along with its needed effects, methylnaltrexone 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

• chills
• diarrhea
• fear or nervousness
• increased sweating
• severe abdominal or stomach pain
• severe or persistent diarrhea
• yawning

For healthcare professionals

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

General adverse events

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

• 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]

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]

Local

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

Frequently asked questions

• Which drugs cause opioid-induced constipation?

Further information

Methylnaltrexone side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Note: Medication side effects may be underreported. If you are experiencing side effects that are not listed, submit a report to the FDA by following this guide.

Medical Disclaimer