Updated March 10, 2014.

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Opioids are a powerful type of pain medication, or analgesic.  The first opioid produced on a large scale was morphine, which is derived from the resin of the opium poppy plant.  Morphine is still used today; however, there are now many other types of opoid pain medications.  Some utilize morphine as the active ingredient, others are synthetic, meaning they work like morphine but are created in a lab and do not contain morphine.

Opioids are frequently used for pain control after surgery, as they are the most powerful pain relievers currently available.  Unfortunately, all opioids, whether they are morphine based or synthetic, have a well-known side effect of causing constipation.

What is Constipation

Constipation is a condition where a person has less than three bowel movements a week, or has bowel movements that are difficult to pass because they are hard and dry.  That said, every individual’s bowel habits are different.  For someone who routinely has two bowel movements a day, having five per week is a dramatic change and may indicate constipation.  For someone who typically has soft stools, hard or painful to pass stools may be a sign of a significant change.

How Opioids Cause Constipation

There are several reasons that the opioid class of medications cause constipation.  These drugs can decrease the movement of food through the intestinal tract, which gives the body more time to remove water from the food.  This can lead to a drier than typical stool.

  It is also believed that opioids may actually increase the amount of water that is absorbed from the GI tract, also leading to drier stool.  These medications may also decrease the urge to have a bowel movement, which again allows more time for the body to remove water from stool.

Causes of constipation after surgery

Preventing Constipation

Ideally, the patient who is taking opioids should work to prevent constipation from happening, rather than treating constipation once it happens.  Constipation can be uncomfortable or even painful, and should be avoided when possible.

There are several ways you can prevent constipation while taking opioids.  First, take no more of the medication than you need as higher doses of opioids lead to a higher risk of constipation.  Hydration is also key in preventing constipation.  Take your medication with water and continue to drink water through the day.  The recommended daily intake of water is typically about 64 ounces, which may not be enough when taking opioids.  Avoid caffeinated beverages as they can increase dehydration and work against your efforts to increase your water intake.

Eating is important, but what you eat can decrease your risk of constipation. Increase your fiber intake by eating fruits and vegetables, preferably as close to their natural state as possible.  A whole orange will do a better job of providing fiber for your diet than orange juice with the pulp removed.  You can also add fiber to your diet with fiber supplements, but remember that adding supplemental fiber can increase constipation if too little water is consumed.  Stool softeners can also help prevent constipation.  If you have recently had surgery, consult your surgeon before using fiber supplements or stool softeners. 

Physical activity, such as walking, has also been shown to decrease the risk of constipation.

Treating Constipation

If you have developed constipation, the advice for preventing constipation still applies to you.  Increasing your water intake is essential, as are dietary changes to add fiber to your diet.

Common Types of Anti-Constipation Treatments:

• Enema
• Stool Softener
• Laxative
• Fiber Supplement

There are many over the counter and prescription treatments for constipation, but if you have recently had surgery, you should consult your physician prior to using them.  Constipation relieving agents vary in how gently or aggressively they treat constipation, and can cause considerable abdominal distress.  Too much medication or overly aggressive treatment can cause cramping, pain and diarrhea.  

Constipation should never be ignored.  It can lead to a more serious form of constipation called fecal impaction, where the hardened pieces of stool must be manually removed.

Source:

Constipation. National Digestive Disease Information Clearinghouse. Accessed February 2014. http://digestive.niddk.nih.gov/ddiseases/pubs/constipation/