What Is Opioid-Induced Constipation?

woman taking a pill
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Opioid-induced constipation (OIC) is diagnosed when people who are taking opioid medications for pain begin to experience constipation on a regular basis. OIC is one symptom of the larger effect of opioids on the digestive system, a condition known as opioid-induced bowel dysfunction (OBD).

Estimates of the number of people who experience OIC with opioid use for chronic non-cancer pain range from approximately 40 to 80 percent.

OIC can cause people to discontinue or take less of the opioid medication that they need for pain relief.

Symptoms of OIC

OIC is diagnosed when a person begins to experience any of the following symptoms after starting to take an opioid medication:

What Causes OIC?

Opioid medications achieve their targeted goal of pain amelioration through their effect on the nervous system. This includes the part of the nervous system known as the enteric nervous system which is responsible for the functioning of the digestive system. Opioid medications thus have the potential for interfering with the working of the entire digestive system, from mouth to anus. These overall effects are reflected in the diagnosis of OBD.

The effects of opioid medications on the working of the large intestine is characterized by the diagnosis of OIC.

Interestingly, as people develop tolerance to their opioid pain medication, the effects on the upper parts of the digestive system may lessen, but this is not typically the case with the constipation that arises from use of these medications.

In the large intestine, opioid medications slow down motility, which is the speed of muscle contractions.

Opioids also affect the secretion and absorption of fluids throughout the large intestine. Thus stool sits longer in the colon, where fluid is drawn out and not replaced, with the result of hard stools and constipation.

Opioid medications also have an impact on the anal sphincter, inhibiting the reflexive action to initiate a bowel movement, another factor leading to constipation, and contributing to the uncomfortable sensations of incomplete evacuation.

Treatment of OIC

In the past, OIC has been treated with the standard recommendations for constipation - laxatives. and increased amount of dietary fiber and fluid, as well as increased exercise. These approaches typically offered limited relief of symptoms.

Newer medications have recently become available which target nerve receptors within the digestive system directly. They appear to do this without interfering with the pain-relieving quality of the opioid medications. These medications include:

  • Amitiza (lubiprostone)
  • Movantik (naloxegol)
  • Relistor (methylnaltrexone)
  • Targin (combination of oxycodone and naloxone/Narcan)

Sources:

Holzer, P. "New approaches to the treatment of opioid-induced constipation" European Review for Medical and Pharmacological Sciences 2008 12:119-127.

Leppert, W. "Emerging therapies for patients with symptoms of opioid-induced bowel dysfunction" Drug Design, Development and Therapy 2015 9:2215-2231.

Nelson, A. & Camilleri, M. "Chronic opioid induced constipation in patients with nonmalignant pain: challenges and opportunities" Therapeutic Advances in Gastroenterology 2015 *:206-220.

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