Alvimopan: what it treats, how it is given, side effects
Last updated September 7, 2026.
**Alvimopan (brand name Entereg) is a peripherally acting mu-opioid receptor antagonist used in the hospital to help your bowels start moving again after bowel surgery.** Opioid pain medicine slows the gut by acting on opioid receptors in the bowel wall. Alvimopan blocks those receptors in the gut but stays out of the brain and spinal cord, so it shortens the period of a sluggish, silent bowel without cutting into your pain relief. The single most important safety point is that this is a short-term inpatient drug only: you get a maximum of 15 doses over no more than 7 days, and you cannot take it if you were already using therapeutic doses of opioids every day for more than 7 days in a row right before surgery.
What does it treat?
Alvimopan is approved to speed the return of upper and lower gut function after partial large or small bowel resection with primary anastomosis, meaning the surgeon removes a segment of intestine and sews the two ends back together. The problem it targets is postoperative ileus: after abdominal surgery the bowel can go quiet for days, so you pass no gas and no stool, your belly swells and feels tight, you feel sick or vomit, and you cannot keep down solid food. That delay is what keeps people in the hospital after the surgery itself went well. Alvimopan shortens the time to the first bowel movement, the first tolerated solid meal, and discharge. It is not used for opioid-induced constipation in people taking long-term opioids at home; that pattern is treated with different drugs such as methylnaltrexone, naloxegol, or naldemedine. There are no combination products that contain alvimopan.
How do you take it?
Alvimopan comes as a 12 mg capsule and is dispensed only inside a registered hospital, so a nurse brings each dose to you rather than you filling a prescription. The label dosing is one 12 mg capsule taken 30 minutes to 5 hours before your surgery, then 12 mg twice a day starting the day after surgery, continued until you leave the hospital or for a maximum of 7 days, whichever comes first. The hard ceiling is 15 doses in total, and no take-home supply is given. The capsule can be given with or without food, though a high-fat meal slows absorption; in practice most people are not eating solids during the first days anyway, so the team gives it with a small sip of water. Because the hospital staff track each dose, missed doses are not something you make up on your own, and doses are never doubled. Tell your nurse right away instead of waiting for the next dose if you get chest pain or pressure, shortness of breath, severe cramping belly pain, or vomiting that will not stop, since the drug may need to be stopped.
Side effects to know
- Common: The effects reported most often on the label are indigestion or upper belly discomfort, a low potassium level on blood tests, back pain, and trouble emptying your bladder, and once the bowel wakes up some loose or urgent stools are expected rather than a problem.
- Serious: Get help right away for chest pain or pressure, arm or jaw pain, sudden shortness of breath, or a cold sweat, because a long-term study in a different patient group found more heart attacks with extended use, which is why alvimopan is limited to 15 in-hospital doses. Also report severe or worsening belly pain with a swollen abdomen and repeated vomiting, or signs of an allergic reaction such as hives, swelling of the face, lips, or throat, or trouble breathing, and the drug should be stopped.
Who should not take it?
You cannot take alvimopan if you were on therapeutic doses of opioid pain medicine daily for more than 7 days in a row immediately before surgery, because that group had more severe stomach and bowel side effects. It is also not recommended if you have severe liver disease or end-stage kidney disease, and its benefit has not been shown after surgery for complete bowel obstruction or with a gastric or pancreatic anastomosis. It is not used in children or teenagers under 18. Tell the surgical team if you are pregnant or might be, since there are no adequate studies in pregnant women and the decision is made case by case, and if you are breastfeeding, since it is not known whether alvimopan passes into human milk; many teams will have you pump and discuss timing. Alvimopan does not block the pain relief from your opioid medicine, and it does not require dose changes for most common medicines, but give the team your full list including anything that affects the kidneys or liver. Alcohol is not a practical issue during treatment because every dose is given in the hospital over a few days, but tell the team honestly how much you normally drink, since alcohol withdrawal after admission changes your whole recovery plan.
When is it an emergency?
Call 911 for chest pain or pressure, pain spreading to the arm, neck, or jaw, sudden trouble breathing, fainting or collapse, or swelling of the face, lips, tongue, or throat with hives. If capsules are swallowed by accident, by a child, or in a larger amount than prescribed, call Poison Control at 1-800-222-1222 right away; there is no specific antidote, and expected effects are severe cramping abdominal pain and diarrhea. While you are recovering, tell your nurse or surgeon the same day about a belly that keeps getting bigger and harder, vomiting that will not stop, no gas and no stool at all as the days pass, a fever, or drainage, redness, or opening at the surgical incision, since those point to a problem with the surgery itself rather than the medicine.
What a Pymander AI doctor consult looks like
Illustrative example, not a real member's messages.
Common questions
What is the maximum amount of alvimopan I can get?
The ceiling is 15 doses of 12 mg, given over no more than 7 days. That works out to one capsule 30 minutes to 5 hours before surgery, then one capsule twice a day starting the day after surgery. If you leave the hospital before day seven, the drug stops at discharge and you do not take any home. There is no higher dose for people who are still not passing gas, and taking more does not make the bowel wake up faster. The limit exists because a long-term study in a different group of patients showed more heart attacks with extended use.
Can I drink alcohol while taking alvimopan?
The question rarely comes up in practice because every dose is given to you in the hospital over a few days, and you will not have a supply at home. There is no specific interaction listed between alvimopan and alcohol. What does matter is telling your surgical team how much you normally drink before the operation. Regular heavy drinking can lead to withdrawal during an admission, which affects your heart rate, blood pressure, and confusion level, and it changes how your pain and recovery are managed.
Is alvimopan safe during pregnancy or breastfeeding?
There are no adequate and well controlled studies of alvimopan in pregnant women, so it is used during pregnancy only if your surgeon judges the benefit worth it for your situation. Tell the team before surgery if you are pregnant or think you might be. For breastfeeding, it is not known whether alvimopan passes into human milk, so this is a conversation to have with both the surgical team and your pediatrician. Because treatment lasts a few days at most, some parents choose to pump and store or discard milk during that window. Do not stop breastfeeding on your own without asking first.
Do I need to take alvimopan with food?
No. The capsule can be given with or without food. A high-fat meal slows how fast and how completely the drug is absorbed, so the hospital usually gives it with a small sip of water rather than with a meal. In the first days after bowel surgery you are often not eating solids anyway, and your team advances your diet on their own schedule. Follow their instructions about eating and drinking rather than timing food around the capsule yourself.
What are the signs of taking too much alvimopan?
Too much alvimopan mainly hits the gut, so expect severe cramping belly pain and heavy diarrhea. In studies, single doses well above the approved amount were taken without lasting harm, but there is no specific antidote and you should not wait to see how it goes. Call Poison Control at 1-800-222-1222 for any accidental or extra dose, including a capsule swallowed by a child. Call 911 instead if there is fainting, trouble breathing, or chest pain. Bring the bottle or the dose information with you if you go in.
Will alvimopan stop my pain medicine from working?
No. Alvimopan works on opioid receptors in the wall of your intestines and does not meaningfully cross into your brain or spinal cord, so your morphine, hydromorphone, or oxycodone still controls pain normally. It also does not trigger opioid withdrawal. The one interaction that truly matters is history rather than a drug pairing: if you took therapeutic doses of opioids every day for more than 7 straight days right before surgery, you cannot receive alvimopan at all, because that group had more severe stomach and bowel side effects. Give your team a complete medicine list anyway, including over the counter products and supplements.