Opioid-Induced Constipation: Causes and Treatment Options

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Opioid-induced constipation is constipation that starts or gets worse when a person begins, changes, or increases an opioid pain medicine. It is one of the most common side effects of these medicines, and unlike drowsiness or nausea, it usually does not fade as the body adjusts. Gastroenterology guidelines treat it in steps: regular laxatives first, then prescription medicines designed to block the opioid's effect on the gut if laxatives are not enough. This page is for adults in Arlington, Annandale, and the rest of Northern Virginia who take opioids after surgery, for an injury, or for long-term pain, and for the people who help care for them.

This article is general education, not medical advice. It does not replace the instructions of the clinician who prescribes your pain medicine.

What opioid-induced constipation is

Opioids relieve pain by acting on receptors in the brain and spinal cord. The same type of receptor, called the mu-opioid receptor, also sits in the nerves that run the digestive tract. A clinical guideline published in Pain Medicine by a European group of gastroenterologists explains what happens there: the bowel makes more contractions that do not push stool forward, and less water and salt move into the gut. Stool travels more slowly, dries out, and becomes hard and infrequent.

The Rome criteria, the standard definitions used for digestive symptoms, define opioid-induced constipation as new or worsening constipation when starting, changing, or increasing opioid therapy, with at least two of the following:

• Straining during more than a quarter of bowel movements
• Lumpy or hard stools more than a quarter of the time
• A feeling of incomplete emptying more than a quarter of the time
• A feeling of blockage in the rectum more than a quarter of the time
• Needing to use fingers or other manual help more than a quarter of the time
• Fewer than three spontaneous bowel movements a week

Loose stools should rarely happen without a laxative. Those criteria are quoted in a 2026 German expert consensus on opioid-induced constipation. The newer Rome V criteria, published in May 2026, made no substantive change to this definition.

Why opioid-induced constipation does not wear off

Many opioid side effects ease after the first days or weeks. Constipation is the exception. The Pain Medicine guideline states that while the pain-relieving effect may lessen with continued use, opioid-induced constipation tends to remain and is not subject to tolerance. The German consensus makes the same point. That is why a person on opioids for more than a short stretch should not assume the problem will settle by itself.

How common it is

Estimates vary with how constipation is measured. The Pain Medicine guideline notes that about half of people taking opioids experience it. Some people are more likely to than others. The German consensus names a prior history of constipation as the most important predictor, and lists female sex, low physical activity, low fluid intake, other illnesses, certain surgeries (especially gynecologic, abdominal, and anorectal), and other constipating medicines as added risk factors.

Who gets opioid-induced constipation

Opioids are prescribed in several very different situations, and the constipation question looks a little different in each:

• After surgery or an injury. A short course of opioids often comes at a time when a person is also moving less, eating differently, and possibly taking other medicines. Several of those things slow the bowel on their own.
• Long-term pain not caused by cancer. Back pain, arthritis, nerve pain, and other chronic conditions are the setting most prescription treatments for opioid-induced constipation were studied in.
• Cancer pain and advanced illness. Constipation here can have several causes at once, and the approach is usually coordinated with the oncology or palliative care team.

Opioids are not the only medicines that slow the bowel. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) lists narcotic pain medicines alongside antacids that contain aluminum and calcium, iron supplements, anticholinergics and antispasmodics, calcium channel blockers, diuretics, some antidepressants, seizure medicines, and Parkinson's medicines. A full medication list is one of the most useful things to bring to a visit.

Opioid-induced constipation is more than infrequent stools

The Pain Medicine guideline uses a broader term, opioid-induced bowel dysfunction, because opioids act along the whole digestive tract. Besides constipation, people may notice bloating, abdominal discomfort, nausea, reflux, or a full feeling after small meals. Opioids can also slow stomach emptying, which is one of the medication causes our gastroparesis page describes.

The Rome classification also lists a separate condition, narcotic bowel syndrome, which Rome V also calls opioid-induced gastrointestinal hyperalgesia. In that condition the main problem is abdominal pain rather than constipation. If belly pain is getting worse while you stay on an opioid or as the dose goes up, say so plainly to your clinician.

Why laxatives come first for opioid-induced constipation

The American Gastroenterological Association (AGA) published its guideline on the medical management of opioid-induced constipation in late 2018 (Crockett and colleagues, Gastroenterology, 2019). It is still the current AGA document on this topic. Its first recommendation is direct: in people with opioid-induced constipation, AGA recommends laxatives as first-line agents.

The European and German documents agree on that order, and the German consensus is candid about why. It says the case for laxatives first rests on indirect evidence, clinical experience, and guideline endorsement, since few high-quality trials were designed to test laxatives in this specific condition. Laxatives are widely available, inexpensive, and familiar, and the newer prescription medicines were approved for people whose laxatives were not enough.

Which laxatives guidelines lean toward

Guidelines do not all name the same products, and the right choice depends on the person, so this is a description rather than a recommendation:

• Osmotic laxatives, which draw water into the stool. The German consensus singles out polyethylene glycol (PEG), also called macrogol, as a favorable first choice because of its safety record and the way it softens stool.
• Stimulant laxatives, which prompt the bowel to contract. The Pain Medicine guideline lists bisacodyl, sodium picosulfate, macrogol, and sennosides as reasonable first choices based on indirect evidence.
• Sugar-based laxatives such as lactulose are generally not favored. Both European documents advise against them for this condition because bacteria ferment them, which can add bloating.

We do not print doses here. Laxative amounts depend on the product, the person, and their other medicines, and they should come from the clinician or pharmacist who knows the full picture.

Fiber, fluids, and movement

The German consensus recommends adequate fluids, fiber, and physical activity where possible as general prevention, because constipation usually has more than one cause. It also cautions that fiber-based bulking laxatives may worsen abdominal distention and are generally not appropriate for preventing or treating opioid-induced constipation on their own. That differs from the usual advice for everyday constipation, which our chronic constipation page covers. Adding a lot of fiber to a bowel that an opioid has already slowed can leave a person more bloated rather than more regular.

Should a laxative start at the same time as the opioid?

Guidelines do not fully agree here. The German consensus says laxatives should start alongside the opioid or no later than the first sign of constipation, with the decision to start ahead of time made case by case, especially for people at higher risk, such as those confined to bed. The Pain Medicine guideline takes a more cautious line: since only about half of people on opioids develop constipation, it calls routine co-prescription for everyone an overtreatment, and suggests adjusting prevention to each person's risk, for example in someone who was already constipated before starting.

Both agree on the practical part. Ask about constipation when an opioid is first prescribed, know what your plan is if it starts, and check in early rather than waiting weeks. The German panel recommends a bowel check before opioids start and again no later than the second week.

Laxatives work only when taken as planned

The German consensus cites a study in which a third of people prescribed a laxative or a prescription treatment for this problem did not take it daily. For many people with opioid-induced constipation, an as-needed laxative taken only once things are bad is not enough to keep up with a medicine taken every day.

Prescription treatments when laxatives are not enough

When constipation persists despite laxatives used correctly, the next class AGA considers is the peripherally acting mu-opioid receptor antagonists, often shortened to PAMORAs. These medicines block opioid receptors in the gut but are designed not to cross into the brain, so they target the constipation without undoing the pain relief. AGA's recommendations for people whose constipation has not responded to laxatives are:

• Naldemedine (Symproic): AGA recommends it over no treatment.
• Naloxegol (Movantik): AGA recommends it over no treatment.
• Methylnaltrexone (Relistor): AGA suggests it over no treatment, a weaker grade of recommendation.

The German consensus describes a similar ladder: a laxative, then a switch to one of these medicines, then trying a different one if the first does not work, and then combining one with a laxative.

What the FDA labels say

The labels on DailyMed, the National Library of Medicine's database of FDA drug labels, set out who these medicines are for and when they should not be used:

• The naloxegol, naldemedine, and methylnaltrexone labels approve them for opioid-induced constipation in adults with chronic pain not caused by cancer, including pain related to prior cancer or its treatment in people who do not need frequent opioid dose increases.
• Methylnaltrexone injection has a second approval: adults with advanced illness or pain caused by active cancer who need opioid dose increases for palliative care.
• All three labels say people who have taken opioids for less than 4 weeks may be less responsive. That is one reason these medicines are less of a fit for a short course after surgery.
• All three are contraindicated in people with a known or suspected bowel obstruction, or at risk of one coming back, because of the potential for a tear in the bowel wall.
• The naloxegol label reports bowel perforations, including fatal cases, in people already at risk, such as those with cancer involving the digestive tract, recent bowel surgery, diverticular disease, or ischemic colitis.
• The labels also warn about opioid withdrawal symptoms, such as sweating, chills, diarrhea, abdominal pain, anxiety, and yawning. The naloxegol label notes that people taking methadone for pain had more digestive side effects in its trials.
• The naloxegol and methylnaltrexone labels direct that maintenance laxatives be stopped before starting, and allow them again if constipation persists after 3 days. Each of these medicines is meant to stop when the opioid stops.

The naloxegol label also says it should not be taken with strong CYP3A4 inhibitors, a group that includes the antibiotic clarithromycin and the antifungal ketoconazole, and that grapefruit should be avoided. Drug interactions are a good reason to keep one pharmacy and one up-to-date medication list.

Medicines AGA made no recommendation on

AGA made no recommendation for or against two other medicines in opioid-induced constipation. Lubiprostone (Amitiza) is FDA-approved for it in adults with chronic non-cancer pain, but its label states that its effectiveness has not been established in people taking diphenylheptane opioids such as methadone. Prucalopride is the other. "No recommendation" means AGA did not take a position either way, not that it found the medicines unsafe.

Do not cut back your pain medicine on your own

Constipation is a common reason people quietly skip doses or stop an opioid early. The German consensus says better education is meant in part to prevent exactly that, because it can leave pain undertreated. The FDA labels for the prescription constipation medicines state that the pain regimen does not need to change before starting them. If the side effects feel worse than the pain, that is a conversation for the prescriber, who can weigh any change to the opioid itself.

Complications of opioid-induced constipation

Leakage that looks like diarrhea

Severe constipation can cause stool leakage. NIDDK explains that large, hard stools can stretch and weaken the rectal muscles, and watery stool that builds up behind the hard stool can then leak out. That can look like diarrhea, and taking an anti-diarrhea medicine for it would make the underlying problem worse. Our fecal incontinence page explains this overflow pattern.

Hemorrhoids and fissures

NIDDK lists straining during bowel movements and chronic constipation among the causes of hemorrhoids, and hard stools can also cause small tears in the anal lining. Bright red blood on the tissue, pain with bowel movements, or a lump near the anus are worth mentioning. Our pages on hemorrhoids and anal fissures cover both.

When to get urgent care

Opioid-induced constipation is usually managed in the office, but a blocked bowel is an emergency. MedlinePlus advises contacting a provider if you cannot pass stool or gas, have a swollen abdomen that does not go away, keep vomiting, or have unexplained abdominal pain that does not go away. If those come on strongly, go to an emergency department or call 911 rather than waiting for an office visit. The PAMORA labels also tell people taking those medicines to watch for severe, persistent, or worsening abdominal pain and to stop and seek care if it develops.

When opioid-induced constipation needs a gastroenterologist

Most people start with the clinician who prescribes the opioid, often a surgeon, pain specialist, oncologist, or primary care physician. A gastroenterologist becomes useful when:

• Constipation continues despite laxatives taken regularly as directed
• The diagnosis is unclear, for example because constipation was a problem before the opioid started
• There is blood in the stool, black stools, unintentional weight loss, or a new change in bowel habits later in life
• Bloating, nausea, or abdominal pain are becoming the main problem
• A colonoscopy or other procedure is planned while you are taking opioids

An opioid does not explain away those signs. They need their own evaluation, and our pages on blood in the stool, black stools, and unexplained weight loss explain when each is urgent. Screening for colorectal cancer also continues on schedule; see our guide to colon cancer screening options.

Opioids and colonoscopy prep

The US Multi-Society Task Force on Colorectal Cancer lists opioid pain medicines among the factors linked to an incomplete colonoscopy prep, because they slow the bowel. If you take opioids regularly, tell the office when the procedure is scheduled, not on the morning of it. Our page on inadequate bowel prep explains why prep sometimes falls short and what can change the second time.

Opioid-induced constipation care in Northern Virginia with GC of NoVA

Gastroenterology Center of Northern Virginia sees adults across Arlington, Annandale, and the surrounding communities with constipation, including constipation linked to pain medicine. Our five gastroenterologists can review your medicines and bowel history, look for other causes, and work with the physician who manages your pain on a plan that keeps both under control. Our page on your first gastroenterologist visit explains what to bring, and a complete medication list, including over-the-counter laxatives and supplements, is the most helpful item on it.

We see patients at our Arlington office at 1715 N George Mason Drive, adjacent to VHC Health, and our Annandale office at 3299 Woodburn Road in the Woodburn Medical complex. To schedule a visit, call Arlington at (703) 522-7476 or Annandale at (703) 560-6106, or learn more at gcofnova.com.

This article is for general education and is not medical advice. Talk with a qualified gastroenterologist about your symptoms, diagnosis, and treatment options.