Narcotic Bowel Syndrome (NBS) and Opioid-induced Constipation (OIC)
Up to 90% of patients with chronic pain receive opioids as a way of treatment to help them obtain some relief from the pain. With the increased use of prescribed opioids in the US due to chronic pain, comes the gastrointestinal complications of narcotic bowel syndrome (NBS) and opioid-induced constipation (OIC). Narcotic bowel syndrome is linked to the central nervous system. NBS can occur in patients with no prior gastrointestinal disorder after they receive high dosages of narcotics due to surgery or chronic pain. The increased dosage of narcotics causes contradictory worsening of abdominal pain as you intake them to decrease pain in other areas. OIC is the most common gastrointestinal side effect of taking opioids.
Opioids affect the entire gut, from the mouth to the anus. The intestines are designed so that muscles can squeeze and then release in order to push stool through your gut. There are several ways that opioids cause constipation and the usual over-the-counter treatment may help very little or may not help at all. Opioid usage slows down the time it takes for food to travel through your intestines by sending messages along the nerves inside your intestines and spine. When your intestines squeeze at both ends of the stool, the stool can't go anywhere which causes OIC or NBS. Sphincters are muscles that separate one part of your gut from another. When the sphincters open, stool passes through. Opioids tighten those muscles so that they only open very little or don't open at all. Your intestines also naturally absorb some water from your stool as it passes through but when the time frame slows down the passage of the stool, it allows the intestines to absorb more water than it should. With that comes a dry and hard stool. All of these things can work together or separately to cause OIC.
NBS or OIC is unlike constipation that may be caused when you eat the wrong food, don't have enough fiber in your diet or aren't drinking enough water. Some symptoms of opioid causing constipation are not having the urge to go, having to push really hard to go at all, feeling like you are not emptying your intestines, a hard and/or dry stool, stomach pain and/or protrusion, pain and cramping in your gut. Eventually, this could cause complete bowel blockage which can be very dangerous. Call your doctor right away if you believe you may have NBS or OIC from opioid usage. If you are just starting to take opioids for chronic pain, be sure to talk with your physician on ways to avoid constipation associated with it. A full history and physical examination are critical. What were the patients' bowel movement patterns before starting to take opioids versus what they are like now? Other causes of constipation should be evaluated and ruled out. It is possible that once the cause of constipation is determined to be due to opioid intake, a patient may have to stay on laxatives as long as they continue to take the opioids. The use of prophylactic anti-constipation agents is the current standard of care.