Entereg (Alvimopan) - Oral


Entereg (alvimopan) is only meant for short-term (15 doses) use in a hospital setting.

What Is Entereg?

Entereg (alvimopan) is a peripherally acting mu-opioid receptor antagonist that promotes faster gastrointestinal (GI) recovery after bowel resection surgery.

Following surgery, opioids are typically used to help manage surgical pain. However, they can temporarily slow or stop bowel function. This can lead to symptoms such as constipation and bloating.

As a mu-opioid receptor antagonist, alvimopan protects the bowel from these effects without reversing the opioid's pain-relieving properties so that you can recover more quickly from surgery.

Entereg is available as a prescription oral capsule. It is only prescribed for use in the hospital.

Drug Facts

Generic Name: Alvimopan

Brand Name(s): Entereg

Drug Availability: Prescription

Administration Route: Oral

Therapeutic Classification: Gastrointestinal agent, opioid antagonist

Available Generically: Yes

Controlled Substance: N/A

Active Ingredient: Alvimopan

Dosage Form(s): Capsule

What Is Entereg Used For?

The Food and Drug Administration (FDA) approved Entereg to treat postoperative ileus in adults following the removal of part of the large or small intestine (partial large or small bowel resection surgery) with a surgical technique that connects two body structures (primary anastomosis).

Ileus is a condition in which the bowel does not work properly. It can slow or stop movement in the intestine, which can cause a blockage. Postoperative ileus occurs after a surgical procedure and is often worsened by opioid use.

As an opioid antagonist, Entereg stops opioids from affecting the intestines so that you are able to pass bowel movements. This aids your recovery from surgery.

How to Take Entereg

You will be given Entereg to take in the hospital only for short-term use—no more than 15 doses. Take the capsule with or without food.


Store Entereg capsules at room temperature (77 F).

Off-Label Uses

Healthcare providers may prescribe alvimopan for conditions not specifically indicated by the FDA (off-label uses).

For example, alvimopan can be used to treat bowel dysfunction in other circumstances, such as:

  • Opioid-induced bowel dysfunction
  • Postoperative ileus following abdominal removal of the uterus (hysterectomy)

How Long Does Entereg Take to Work?

In clinical trials, people taking Entereg began to see gastrointestinal recovery about 48 hours after surgery.

What Are the Side Effects of Entereg?

This is not a complete list of side effects, and others may occur. A healthcare provider can advise you on side effects. If you experience other effects, contact your healthcare provider. You may report side effects to the FDA at fda.gov/medwatch or 1-800-FDA-1088.

Common Side Effects

The most common side effects in people undergoing bowel resection surgery taking Entereg were:

Severe Side Effects

Tell your healthcare provider immediately if you have serious side effects.

The above-listed side effects can become severe if left untreated. Be sure to tell your healthcare provider if you notice any new symptoms or changes in how you feel after taking Entereg.

Long-term use of Entereg can increase the risk of a heart attack. Therefore, this medication is only available for restricted short-term use under a Risk Evaluation and Mitigation Strategy (REMS) program.

Taking opioids within the last seven days of receiving Entereg can make you more prone to severe adverse reactions. Tell your healthcare team about recent opioid use, if applicable.

Report Side Effects

Entereg may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your healthcare provider may send a report to the FDA's MedWatch Adverse Event Reporting Program or by phone (1-800-332-1088).

Dosage: How Much Entereg Should I Take?

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The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For oral dosage form (capsules):
    • For restoring normal bowel function after bowel surgery:
      • Adults—12 milligrams (mg) 30 minutes to 5 hours before the surgery, then 12 mg two times a day starting from the day after surgery up to a maximum of 7 days or until discharge.
      • Children—Use and dose must be determined by your doctor.


Entereg has not been studied enough in pregnancy to determine whether it is safe or not. If you are pregnant, talk to your healthcare provider to determine whether or not Entereg is a safe option for you. It is unknown if the medication passes into breast milk.

Missed Dose

This medication will be provided to you by a trained healthcare provider in the hospital, so missed doses are not likely to occur.

Overdose: What Happens If I Take Too Much Entereg?

Doses of this medication will be provided to you while in the hospital. Therefore, an overdose is unlikely.

There is no specific antidote for overdoses with Entereg. Treatment would likely be symptomatic and supportive. In clinical trials, single doses of up to 120 milligrams and multiple doses of up to 48 milligrams for seven days were given to otherwise healthy individuals and were well tolerated.

What Happens If I Overdose on Entereg?

If you think you or someone else may have overdosed on Entereg call a healthcare provider or the Poison Control Center (1-800-222-1222).

If someone collapses or isn't breathing after taking Entereg, call 911 immediately.


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It is very important that your doctor check your progress at regular visits to check for any problems or unwanted effects that may be caused by this medicine.

Taking this medicine for more than 15 doses may increase the risk for a heart attack. Patients should not receive more than 15 doses of this medicine.

Make sure your doctor knows if you have been using narcotic pain relievers (e.g., codeine, morphine, or Dolophine®) in the past 7 days before you start taking this medicine. Using this medicine together with narcotic pain relievers may increase the chance of unwanted effects.

What Are Reasons I Shouldn’t Take Entereg?

Do not take Entereg if you are allergic to alvimopan or other ingredients of Entereg.

You should also inform your healthcare provider if you have taken therapeutic doses of opioid pain medication for more than seven consecutive days immediately before taking Entereg.

This medication should not be prescribed for more than 15 doses.

What Other Medications Interact With Entereg?

No clinically significant drug-drug interactions have been identified with Entereg.

What Medications are Similar?

Other peripherally acting mu-opioid receptor antagonists used to treat opioid-induced constipation are:

  • Relistor (methylnaltrexone): Oral and subcutaneous (under the skin) injections
  • Movantik (naloxegol): Oral
  • Naldemadine: Oral

These medications differ from Entereg in that they can be used outside the hospital for a longer time, whereas Entereg is only used short-term in the hospital.

Frequently Asked Questions

  • What is Entereg used for?

    Entereg is used to treat postoperative ileus after small or large bowel resection surgery. It can also be prescribed "off-label" to treat opioid-induced constipation or postoperative ileus following other abdominal surgery.

  • How does Entereg work?

    Painkillers called opioids that are used during and after surgery can slow or stop movement in the intestines (GI motility). This can cause GI symptoms like constipation and delay the return of normal bowel function after surgery.

    Entereg works by blocking (antagonizing) the effects of opioids on GI motility and enzymes and fluids that help transport food through the body (secretions) but does not affect the central pain-relieving effects of opioids.

  • What side effects can I expect while taking Entereg?

    The most common side effects of Entereg are indigestion, nausea, vomiting, abdominal pain, and diarrhea.

    Before starting Entereg, tell your healthcare if you've taken opioids within the previous seven days. Prior opioid use during this time can increase your risk of GI-related side effects.

  • How long will I need to take Entereg?

    You will only be given Entereg while in the hospital for up to seven days. Entereg is only indicated for short-term use. You will not receive more than 15 doses during treatment. This medication is not prescribed for use outside of the hospital.

How Can I Stay Healthy While Taking Entereg?

Follow your healthcare provider's instructions and take all medications as prescribed following your surgery to help ensure a smooth recovery.

After surgery, your bowel functioning may temporarily slow or stop, especially if you are taking opioid pain medication. Entereg can be used to help protect your bowels from this side effect. You will only take it while in the hospital.

Once discharged, you should continue to take care of yourself while recovering. Ask your healthcare provider about diet recommendations and when you can start to increase your physical activity. Remember to be patient and not push yourself too hard as you heal.

Medical Disclaimer

Verywell Health's drug information is meant for educational purposes only and is not intended to replace medical advice, diagnosis, or treatment from a healthcare provider. Consult your healthcare provider before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.

5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Food and Drug Administration. Entereg label.

  2. Kurz A, Sessler DI. Opioid-induced bowel dysfunction: pathophysiology and potential new therapies. Drugs. 2003;63(7):649-671. doi:10.2165/00003495-200363070-00003

  3. Viscusi ER, Gan TJ, Leslie JB, et al. Peripherally acting mu-opioid receptor antagonists and postoperative ileus: mechanisms of action and clinical applicability. Anesth Analg. 2009;108(6):1811-1822. doi:10.1213/ane.0b013e31819e0d3a

  4. Prescribers' Digital Reference. Alvimopan - drug summary.

  5. Berger NG, Ridolfi TJ, Ludwig KA. Delayed gastrointestinal recovery after abdominal operation - role of alvimopan. Clin Exp Gastroenterol. 2015;8:231-235. doi:10.2147/CEG.S64029

By Carrie Yuan, PharmD
Carrie Yuan PharmD is a clinical pharmacist with expertise in chronic disease medication management for conditions encountered in primary care.