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by C.H. Weaver M.D. Medical Editor 8.2021

What is constipation?

Constipation is difficulty passing stools or a decrease in number of stools. It may be accompanied by gas, abdominal cramping or pressure in the lower abdomen. Constipation may lead to stool impaction, a severe form of constipation where the stool will no longer pass through the colon or rectum.

What causes constipation?

Constipation is caused by a slowing of the intestinal activity. The normal wave-like action of the intestines, called peristalsis, serves to continually move stools out of the body. When peristalsis slows, the stools become hard, dry and difficult to pass.

Constipation can have a number of causes including:

  • Pain medications
  • Chemotherapy drugs
  • Decreased activity
  • Poor diet
  • Inadequate fluid intake

Chemotherapy drugs can cause either an increase or decrease in peristalsis. An increase in intestinal activity may cause stools to travel faster and be less formed, resulting in cramping and/or diarrhea. A decrease in intestinal activity may cause stool to travel slower, becoming hard and dry and more difficult to pass, which is constipation.

What are the symptoms of constipation?

Some symptoms of constipation include:

  • A sustained change in frequency of bowel movements from your normal. There is no “normal” schedule for bowel movements; everyone’s schedule is different. If you normally move your bowels once per day, a change may be every 2nd or 3rd day.
  • Hard, difficult to pass bowel movements. You may pass small, marble-like pieces of stool without a satisfactory elimination.
  • Cramping and/or flatulence (gas).

How can constipation be prevented?

It is easier to prevent constipation with lifestyle changes than to treat it once it happens. Here are some tips.

  • Drink plenty of water. Taking in enough fluids keeps the stool soft. Try to drink 6-8 glasses (8 oz.) of fluid a day.
  • Eat foods high in fiber, such as fruit, vegetables and beans. High-fiber foods stimulate the intestines to move.
  • Avoid cheese, meat, processed food and other low fiber foods that cause constipation.
  • Exercise daily. Exercise helps stimulate digestion and prevent constipation. Moderate activity such as walking will help.

It may also help to keep track of your bowel movement schedule so that you can learn which lifestyle measures work best for you. If you miss a bowel movement, try increasing your fluid intake or adjusting your diet. Call your doctor if your bowels have not moved in two days.

How is constipation treated?

If you have tried the above lifestyle changes and are still experiencing constipation, your doctor may prescribe laxatives. Laxatives are available in liquid, tablet, gum, powder and granule forms. There are several different kinds that work in different ways.

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Laxatives should only be used for a short period of time in order to retrain the bowel to pass stools naturally. If used continually, you may become dependent on laxatives. In most people, slowly stopping use of the medication will restore the colon’s natural ability to contract.

Opiate Induced Constipation

For constipation caused by opioid pain medications (such as morphine, codeine, oxycodone, and fentanyl), laxative use often continues for as long as the patient is taking the pain medication. TheAGA: New Opioid-Induced Constipation Management Guidelines Released 10/2018

The American Gastroenterological Association (AGA) has issued new guidelines on the medical management of opioid-induced constipation (OIC).

“These guidelines presume that patients have been appropriately diagnosed and that they have either a prolonged requirement or dependence on opioids,” write the authors. “Therefore, one of the first steps to managing patients with OIC is to ensure that the indication for opioid therapy is appropriate, that patients are participating in a pain management program (ideally in conjunction with a pain specialist), and that they are taking the minimum necessary opioid dose.”

In the management of OIC, the new guidelines state the following:

  • In patients with OIC, the use of laxatives as first-line agents is recommended.
  • In patients with laxative refractory OIC, naldemedine is recommended over no treatment.
  • In patients with laxative refractory OIC, naloxegel is recommended over no treatment.
  • In patients with laxative refractory OIC, methylnaltrexone is suggested over no treatment.
  • The AGA makes no recommendation for the use of lubiprostone in OIC.
  • The AGA makes no recommendation for the use of prucalopride in OIC.

Addressing their recommendations on newer agents (intestinal secretagogues, selective 5-HT agonists), the guideline panel writes that given the lack of published data on long-term use, additional studies are needed to establish the benefits of these drugs.

Relistor® (methylnaltrexone bromide): For patients who develop constipation as a result of opioid pain medications (such as morphine, codeine, oxycodone, and fentanyl), Relistor provides another approach to treating constipation. Relistor acts by blocking the activity of opioids in the gastrointestinal tract without blocking the pain-relieving effects of opioids in the central nervous system.


  1. American Gastroenterological Association Institute Guideline on the Medical Management of Opioid-Induced Constipation
  2. Thomas J, Karver S, Austin G, et al. Methylnaltrexone for opioid-induced constipation in advanced illness. New England Journal of Medicine. 2008;358:2332-2343.