What is Opioid-Induced Constipation ?

Opioid-induced constipation, or OIC, is a common side effect that impacts between 40% to 60% of patients who take opioids for non-cancer related pain. To prevent this from occurring, laxatives are often given at the same time as the opioid. If a patient still ends up with OIC, they can use both medication and other therapies to manage it. OIC symptoms can show up right when a patient starts taking the opioid or they could appear slowly over time. Alongside constipation, patients may also experience stomach-related side effects like nausea, vomiting, bloating, stomach pain, and straining.

Many patients who develop constipation due to opioids end up stopping the drug therapy because they can’t handle the side effects on their digestive system. Once constipation has developed due to opioid use, treatment to alleviate the constipation can be slow and may not always completely relieve the constipation.

What Causes Opioid-Induced Constipation ?

Opioids are a type of medication that can slow down digestion in the stomach and intestines. This can delay how quickly other medications are absorbed into the body and cause more fluid to be absorbed, leaving less in the intestines. This leads to the stool becoming hard and can cause constipation.

Many people who take opioids and struggle with constipation often report difficulty going to the bathroom and feeling like they haven’t fully emptied their bowels. Opioids can also increase the tension in the anal sphincter, the muscle that controls the opening of your anus, which can make it harder to have a bowel movement.

It’s also important to know that if you’re having problems with bowel blockage, this increase in muscle tension could be a contributing factor. In addition, opioids can slow down the release of digestive juices from the pancreas and bile (a fluid that helps digest fat) from the liver, which can delay digestion.

Risk Factors and Frequency for Opioid-Induced Constipation

Opioid-induced constipation, often referred to as OIC, is commonly experienced by more than 40% to 60% of patients without cancer who are given opioids. Research has found that people who are more likely to get OIC are usually older, female, and unemployed.

Signs and Symptoms of Opioid-Induced Constipation

Opioid-induced constipation can lead to several uncomfortable symptoms. These include:

Feeling bloated
Constipation
Diarrhea
Nausea and vomiting
Alternating between constipation and diarrhea
Fecal impaction, which may require manual removal
Decreased quality of life

A doctor’s exam might show that your belly is slightly swollen. The doctor might also find that you have a blockage of stool during a rectal exam.

Testing for Opioid-Induced Constipation

The Rome IV criteria is a set of standards often used by doctors to diagnose functional constipation, a common digestive issue. According to these criteria, you might have functional constipation if, for the past three months, you’ve experienced at least two of the following:

Passing hard stools at least 25% of the time when you use the bathroom
Feeling like you have to push hard at least 25% of the time when you have a bowel movement
Feeling like you haven’t completely emptied your bowels at least 25% of the time after a bowel movement
Having fewer than 3 bowel movements in a week
Needing to assist the process by manually helping to move or remove your stools at least 25% of the time

Apart from the Rome IV criteria, doctors might also use the Bristol Stool Scale. This tool classifies the shape and consistency of your stool into seven categories. The first two types indicate hard stools, which may be a sign of constipation. Types 3 and 4 are considered normal. If your stools fall into categories 5, 6, or 7, they are loose and could indicate diarrhea.

Usually, doctors don’t need to use imaging tests (such as X-rays or CT scans) to diagnose constipation. However, they will pay close attention to any warning signs or “alarm symptoms”. These include unexpected weight loss, positive results for hidden (“occult”) blood in your stools, a shortage of iron in your blood (as this can indicate anemia), and having a family history of colon cancer.

Treatment Options for Opioid-Induced Constipation

To prevent constipation, a healthy diet rich in fiber and ample fluid intake are recommended. Regular physical exercise is also beneficial. As a part of their routine, healthcare workers who prescribe opioids for pain also need to consider preventative strategies against constipation. A variety of laxatives can be an initial form of treatment. However, bulk-forming laxatives, like psyllium, which increase the size of the stools, aren’t generally advisable. These laxatives make the stools bulkier, which leads to stretching of the colon and increased waves of muscle contractions that push the contents of the gut forward, known as peristalsis. Yet, this texture of stool can actually worsen abdominal pain and may even cause bowel obstruction on some occasions, as opioids retard peristalsis.

A common treatment plan for opioid-induced constipation often includes a stimulant such as senna or bisacodyl, sometimes combined with something known as a ‘stool softener’ like docusate, or alternatively, an osmotic laxative such as polyethylene glycol could be given daily. Stool softeners are useful to prevent constipation rather than treating it once established. A saline laxative like magnesium citrate could be another addition to your arsenal of laxatives, as it usually works swiftly, often beginning to take effect in less than 3 hours. If the commonly used laxatives don’t work, newer medications such as methylnaltrexone could be options.

Methylnaltrexone bromide is used to treat opioid-induced constipation. Because it doesn’t cross what’s known as the ‘blood-brain barrier’, it doesn’t lead to symptoms of opioid withdrawal. Subcutaneous methylnaltrexone has shown better results at reversing opioid-induced constipation than lubiprostone, naloxegol, and oral methylnaltrexone. However, methylnaltrexone is not advisable for patients suffering from peptic ulcer disease, diverticulosis, colon cancer, or obstruction.

Lubiprostone works by increasing fluid secretion in the GI tract, enhancing muscle contractions and speeds passage of the bowel, thus helping to alleviate constipation caused by opioids.

Medications like naloxegol, alvimopan, and naldemedine are also available for treating opioid-induced constipation. Lubiprostone is also approved for treatment in patients suffering non-cancer pain and those with cancer. It’s important to consult with your doctor to determine the best course of action for managing your symptoms.

The following conditions could be potential medical issues:

Colonic obstruction (blockage in the colon)
Crohn’s disease (a type of inflammatory bowel disease)
Diverticulitis (inflammation or infection in the diverts in the wall of the colon)
Hypopituitarism (a condition in which the pituitary gland does not produce normal amounts of some or all of its hormones)
Hypothyroidism (a condition in which your thyroid gland doesn’t produce enough certain crucial hormones)
Ileus (disruption of the normal propulsive ability of the gastrointestinal tract)
Intestinal motility disorders (disorders that affect the bowel’s ability to work properly)
Irritable bowel syndrome (a common disorder that affects the large intestine)
Large bowel obstruction (blockage in the large intestine)
Ogilvie syndrome (a disorder that affects the ability of the colon to move material through it)

Preventing Opioid-Induced Constipation

When a doctor prescribes an opioid painkiller, it’s essential to also consider ways to prevent constipation, a common side effect of this type of medication. This can be done by making a few lifestyle changes like eating a diet rich in fiber, drinking plenty of water, regularly exercising to help your bowels stay active, limiting the use of other painkillers, and using laxatives. Docusate or polyethylene glycol can be used as alternatives to the traditional laxative milk of magnesia. These steps should be put into action at the same time as you begin taking the opioid medication and carried out for as long as you’re under treatment.

Many different foods are packed with fiber and can help combat constipation. You could consider adding fruits such as apples, bananas, prunes, pears, or raspberries to your diet, or vegetables like string beans, broccoli, spinach, kale, squash, lentils, peas, or beans. Other fiber-rich options include most types of bran products (like certain cereals) and nuts. However, it’s important to remember not to consume more than 25-30 grams of fiber per day as this could cause bloating.