Opioids and Your Gut

Opioid medications are often prescribed for chronic pain, and their use is widespread. One of the main side effects of the drugs is constipation. Studies show that up to 47 percent of people on the medicines will experience opioid-induced constipation (OIC).

Constipation is the slow movement of feces through the large intestine. The longer the transit time of stool in the large intestine, the greater the fluid absorption and the drier and harder the stool becomes.

“OIC is development of constipation in association with the use of opioid medications,” said David A. Johnson, M.D., professor of medicine and chief of gastroenterology at the Eastern Virginia Medical School in Norfolk. “OIC can happen even at very low doses of medication.”

Medications for pain are opioid agonists. They mimic the natural opiates found in your body, attaching to opioid receptors and stopping the transmission of pain messages to the brain.

Some of the medications in this class that are prescribed frequently are codeine, fentanyl (Actiq, Duragesic and others), hydrocodone (by itself or with acetaminophen), hydromorphone (Dilaudid), meperidine (Demerol), and oxycodone (Oxycontin).

“Opioid receptors occur throughout the brain, spinal cord, and viscera, including the gut,” said Katherine Galluzzi, DO, professor and chair in the Department of Geriatrics at the Philadelphia College of Osteopathic Medicine. “The opioid that is providing analgesia for the patient will also bind to intestinal mu receptors and may slow down or halt normal bowel function. The result is constipation.”

The symptoms closely resemble those of functional constipation that occurs even without medications. People with OIC will see a change in baseline bowel habits when opioid medications are started, such as:

  • reduced bowel movement frequency (less than two or three a week);
  • more straining while trying to defecate;
  • harder stool consistency;
  • a feeling of not emptying the bowels completely; and
  • bloating, gas, and abdominal pain that is relieved by a bowel movement.

“There is a lot of overlap between OIC and functional constipation,” said Elizabeth John, M.D., of the department of Internal Medicine at Rutgers Robert Wood Johnson Medical School in New Brunswick, New Jersey. “The highlighted difference is that the changes coincide with starting opioid medicines. Any changes in bowel habits after starting opioids should definitely be brought to the attention of your health-care providers.”


Risk Factors

The main risk factor for OIC is, obviously, the use of opioid medications, but some other variables can further increase the likelihood of bowel concerns.

OIC can be a huge problem in people over 70, especially women. Seniors may be on other medications that also can cause constipation. They are often more sedentary, and their diets may be lower in fiber, another issue with constipation in all ages. As for all of us, exercise or walking can help increase bowel efficiency in older people.

“It should be recognized that this is a very common condition,” said Johnson. “It is a constellation of symptoms coming from a worsening of gastrointestinal symptoms. OIC needs to be identified early when it arises, and by anticipating this, we will be able to quickly address and rectify the side effects.”


Management Starts at Prescription

The management of OIC starts when your health-care provider hands you the prescription. When a person is first prescribed an opioid medication, both you and your physician needs to anticipate that constipation can occur.

“You both need to sit down and discuss what should be done in what order if constipation was to occur,” said Charles E. Argoff, M.D., director of the Comprehensive Pain Center at Albany Medical Center in Albany, New York. “When people don’t get guidance upfront, they don’t know what is or isn’t normal. Having the talk when the prescription is made is more efficient, and people always feel better when they know what to expect.”

Make sure your provider knows what your current bowel habits are before you start medication. This not only helps establish a baseline to compare with any concerns you have later on, but also to set realistic goals for return of bowel function should OIC be diagnosed. After all, daily bowel movements may not be a good target if you normally only go every other day.

Also have a list of all medications, supplements, and vitamins you are currently taking. Many drugs can cause constipation on their own, and the use of opioids may make that worse.

Among the classes that you should be aware of:

  • antidepressants, especially tricyclic antidepressants such as amitriptyline (Elavil) and imipramine (Tofranil);
  • antiseizure medications including phenytoin (Dilantin) and carbamazepine (Tegretol);
  • iron supplements; and
  • calcium-channel blocking drugs often used in heart disease such as diltiazem (Cardizem) and nifedipine (Procardia).



Many of the medications’ side effects may lessen the longer you take them. For example, the drowsiness that means you shouldn’t drive or operate heavy machinery can go away over time. OIC doesn’t tend to do that.

Although constipation is seldom life-threatening, there are some complications that you should be aware of. Go immediately to see a physician if you have rectal bleeding, intense abdominal pain, nausea, vomiting, and unplanned weight loss.

“You can get an impaction of feces in the colon with blockage related to reduced bowel function,” said Johnson. “They can have serious consequences such as perforation of the bowel. When you have severe pain and distention and can’t pass gas, you need to get to an emergency room right away.”



Galluzzi thinks that preventative measures should begin at the start of medication use. “I have a ‘not-so-golden-rule’ that states the person who writes the prescription for any opioid should also write prescriptions for a laxative and stool softener because you can almost bet your patient is going to have trouble,” she said. “For most medicine-induced side effects, we wait until we see them to treat. That isn’t the case in OIC.”

The prevention and early treatment of OIC generally follows the same path you see in functional constipation. The first interventions are usually an increase in fluid intake and higher dietary fiber.

“I would suggest a liter or more of water every day,” said Galluzzi. “Lots of people think that includes soda, coffee, tea, or sports drinks. Caffeine can actually remove fluids and should be avoided.”

Drinking that much water can be boring. Water diffusers are an option. Put water in the bottom of the glass, and fill the top with berries, lemon slices, orange slices, cucumbers, or other favorite fruits and vegetables to flavor the water naturally.

Hot lemon water instead of tea to wake up is another suggestion. Just a squeeze of orange or lemon juice in a pitcher of water is useful in flavoring water.

Dietary fiber is another treatment that is used early in OIC. It is available from many natural sources including fruits, vegetables, and cereals. Dietary fiber supplements are also available such as psyllium (Metamucil) and methylcellulose (Celevac). They bulk up the stool so it retains more water, making it easier to move through the intestines.

Exercise has also been shown to help alleviate constipation. However, before starting an exercise regimen, talk to your doctor to make sure fitness options you choose won’t worsen any preexisting medical conditions that you have.


Over-the-counter Medications

Other over-the-counter medications can also be used both in prevention and early treatment. You and your doctor can discuss the following options.

  • Stool softeners make the stool easier to pass. Ducosate (Colace) is one example.
  • Lubricants/emollients soften the feces and prevent water absorption. Mineral oil is often used.
  • Hydrating agents increase the water content of the stool, making it softer and easier to pass. Polyethylene glycol (Miralax) and sodium phosphate (Fleet enemas) are examples.
  • Stimulants increase the contractions that move stools forward. Examples include biscadyl (Dulcolax) and senna.

Argoff notes that that none of these suggestions have been shown to work in OIC. While they have been routinely recommended for years, there are no clinical trials establishing their usefulness.

He stresses that this doesn’t mean over-the-counter medications would not be a good option. The drugs, as well as hydration, diet, and exercise, are all good general suggestions. If they don’t quickly result in better bowel function, then it’s time to talk to your physician or other health-care provider.


Newer Medications

A few newer medications can be prescribed if other treatments are unsuccessful. Methylnaltrexone (Relistor), naloxegol (Movantik), and alvimopan (Entereg) work as opioid receptor antagonists. The opioid pain medications occupy receptors throughout the body. The antagonist medications essentially kick the opioid molecules off the receptors in the gut while not affecting those in the brain. The pathway for blocking pain is maintained while those slowing down the gut are replaced, letting the colon speed back up.

“When you are on an opioid medication, you are your own best advocate,” said John. “Physicians try to keep track of their individual patients, and while they do a good job keeping track of their individual patient’s medications, it is important for you to bring your own list of medications as well as a log of any changes you have experienced since you started or altered these medications.”


Osteopathic Interventions

Osteopathy is a system and philosophy of health care that believes in the healing power of the body. It shares many of the same goals as traditional medicine, but it places more emphasis on the relationship between the organs and the musculoskeletal system. It also focuses on treating the whole individual rather than just the disease.

“Osteopathic physicians have found over and over that one of the best ways to treat constipation of any kind is through osteopathic manipulative medicine,” said Galluzzi. “I don’t think these are used enough.”

Among her suggestions are rib raising, which works to reset the nervous system. It is thought to rebalance the autonomic nervous system that regulates the internal organs and its parasympathetic subsystem that slows them down. Another procedure is a mesenteric lift, which compresses the abdomen to drain lymph (the fluid that circulates throughout the lymphatic system) and blood from the colon. Also, doming the diaphragm and colonic stimulation are thought to work directly to speed up transit time of feces through the colon and produce bowel movements.

“The important part to remember is if you are benefitting from the opioid pain medication, you don’t have to stop because of severe constipation,” said Argoff. “There are medical and non-medical strategies that can help. If your health-care provider doesn’t bring it up, ask what they suggest. Hopefully, that dialog early on will lead to better outcomes.”

Kurt Ullman is a medical writer and a registered nurse. He has worked as a nurse, mostly in psychiatry, and as a staff writer and editor in radio, television, magazines, and newspapers. 

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