May 23, 2017
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Relistor Patient Information Including Side Effects

Brand Names: Relistor

Generic Name: methylnaltrexone (Pronunciation: METh IL nal TREX own)

What is methylnaltrexone (Relistor)?

Methylnaltrexone is a special narcotic drug that blocks certain effects of other narcotic medicines.

Methylnaltrexone reduces constipation caused by narcotic medications that are often used to treat pain in people with terminal illness.

Methylnaltrexone works by preventing this side effect without reducing the pain-relieving effects of the narcotic.

Methylnaltrexone is usually given after laxatives have been tried without successful treatment of constipation.

Methylnaltrexone may also be used for purposes not listed in this medication guide.

What are the possible side effects of methylnaltrexone (Relistor)?

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have severe or ongoing diarrhea, stomach pain that will not go away, black or bloody stools, coughing up blood, or nausea or vomiting that are new or worsening symptoms.

Less serious side effects may include:

  • stomach pain, gas;
  • mild nausea or diarrhea;
  • dizziness; or
  • increased sweating.

This is not a complete list of side effects and others may occur. Tell your doctor about any unusual or bothersome side effect. You may report side effects to FDA at 1-800-FDA-1088.

Read the Relistor (methylnaltrexone bromide injection) Side Effects Center for a complete guide to possible side effects

What is the most important information I should know about methylnaltrexone (Relistor)?

You should not use this medication if you are allergic to methylnaltrexone, or if you have a blockage in your stomach or intestines.

Before you use methylnaltrexone, tell your doctor if you have severe or ongoing diarrhea.

Prepare your dose in a syringe only when you are ready to give yourself an injection. After loading a syringe, if you cannot give the injection right away keep it at room temperature and use it within 24 hours.

Methylnaltrexone may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert.

Side Effects Centers

Report Problems to the Food and Drug Administration


You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.

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