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Entereg Side Effects

Generic Name: alvimopan

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

In Summary

More frequent side effects include: constipation. See below for a comprehensive list of adverse effects.

For the Consumer

Applies to alvimopan: oral capsule

Along with its needed effects, alvimopan (the active ingredient contained in Entereg) 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 alvimopan:

More common
  • Acid or sour stomach
  • belching
  • bloated
  • convulsions
  • decreased urine
  • difficulty having a bowel movement (stool)
  • dry mouth
  • excess air or gas in stomach or intestines
  • full feeling
  • heartburn
  • increased thirst
  • indigestion
  • irregular heartbeat
  • loss of appetite
  • mood changes
  • muscle pain or cramps
  • nausea or vomiting
  • numbness or tingling in hands, feet, or lips
  • pale skin
  • passing gas
  • shortness of breath
  • stomach discomfort, upset, or pain
  • troubled breathing with exertion
  • unusual bleeding or bruising
  • unusual tiredness or weakness
Less common
  • Decrease in frequency of urination
  • decrease in urine volume
  • difficulty in passing urine (dribbling)
  • painful urination

Some side effects of alvimopan 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 alvimopan: oral capsule


Hematologic side effects including anemia (5.2% to 5.4%).[Ref]


Genitourinary side effects have included urinary retention (3.2% to 3.5%).[Ref]


Gastrointestinal side effects have included constipation (4% to 9.7%), flatulence (3.1% to 8.7%), and dyspepsia (5.9% to 7%).[Ref]


Metabolic side effects have included hypokalemia (6.9% to 9.5%).[Ref]


Musculoskeletal side effects have included back pain (3.3% to 3.4%).[Ref]


1. "Product Information. Entereg (alvimopan)." GlaxoSmithKline, Research Triangle Park, NC.

Some side effects of Entereg may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

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.