OPIOD INDUCED CONSTIPATION

opioids often cause constipation, or opioid-induced constipation (OIC). OIC is an uncomfortable side-effect that occurs in many patients who receive opioid treatments to relieve pain.

How do opioids cause constipation?

Opioids are effective pain relievers, but often have the side effect of constipation. These medicines affect the gastrointestinal tract in a variety of ways. Opioids increase the amount of time it takes stool to move through the gastric system. They increase nonpropulsive contractions in the middle of the small intestine (jejunum) and decrease longitudinal propulsive peristalsis - motions critical to moving food through the intestines. This results in food that fails to travel through the digestive tract. Opioids are also able to partially paralyze the stomach (gastroparesis) so that food remains in the digestive organ for a longer period of time. Additionally opioids reduce digestive secretions and decrease the urge to defecate.

What symptoms are associated with OIC?

Several physical and other symptoms are prevalent in sufferers of opioid-induced constipation (OIC). Physicians usually will gather patient history information to check for standard problems associated with constipation such as too little fiber and fluid intake, too little exercise, underlying medical problems, and current medications. Be prepared for a physical assessment that requires oral, abdominal, and digital anorectal examinations.

Common physical symptoms of OIC include:

Stools that are hard and dry
Difficulty such as straining, forcing, and pain when defecating
A constant feeling that you need to use the toilet
Bloating, distention, or bulges in the abdomen
Abdominal tenderness

Other symptoms of OIC include:

Feeling and being sick
Tiredness and lethargy
Appetite loss
Feeling depressed

Treatment options for OIC

Although opioids are very effective for treating and managing pain, their use frequently results in opioid-induced constipation (OIC). Treatment options for OIC may be as simple as changing diet or as complicated as requiring several medicines and laxatives.

How can changing lifestyle factors treat OIC?

Changing lifestyle factors is usually the first recommendation that physicians make for the prevention or treatment of constipation. This includes:

Increasing dietary fiber
Increasing fluid intake
Increasing exercise or physical activity
Increasing time and privacy for toileting
Changes in lifestyle, however, may not be possible for many patients. In addition, these changes may be ineffective in treating OIC. If there is a concurrent underlying disease or medicine that is causing constipation, the disease may need to be treated separately or another treatment regimen may have to be considered.

What drugs or medicines treat OIC?

OIC treatment usually requires additional medicines to be prescribed along with the opioid painkillers that are causing the constipation. Withholding the opioid treatment is ill-advised because it results in a decrease in the patient's quality of life. Often, laxatives and/or cathartics are prescribed at the same time as the opioid painkillers so that treatment for the constipation beings immediately. A cathartic accelerates defecation, while a laxative eases defecation, usually by softening the stool; some medicines are considered to be both laxatives and cathartics.

For the treatment of OIC, doctors may prescribe:

Osmotic laxatives - increase the amount of water in the gut, increasing bulk and softening stools.
Emollient or lubricant cathartics - soften and lubricate stools.
Bulk cathartics - increase bulk and soften stools.
Stimulant cathartics - directly counteract the effect of the opioid medications by increasing intestinal motility, helping the gut to push the stools along.
Prostaglandins or prokinetic drugs - change the way the intestines absorb water and electrolytes, and they increase the weight and frequency of stools while reducing transit time.
Other medicines block the effects of opioids on the bowel to reverse opioid-induced constipation.
Although the treatments listed above are usually successful in treating OIC, sometimes a physician will recommend rectal intervention. As discussed, prophylaxis with laxatives are/or cathartics is considered usual - as some clinicians assume [constipation] to be virtually universal in patients who are prescribed opioid analgesics1.

Rectal interventions are indicated if the appropriate oral measures have been ineffective2. Rectal intervention means the following treatments:

Suppositories
Enemas (micro and larger volume)
Rectal irrigation (sometimes known as colonic irrigation)
Manual evacuation
The first choice rectal intervention for uncomplicated constipation is glycerine suppositories2. If these are ineffective, then a stimulant enema might be administered. Oral and rectal stimulant laxatives should be avoided if there is possible or proven bowel obstruction. Gentle rectal measures can sometimes be effective in emptying the rectum and lower colon. Oral softening agents are useful if the obstruction is incomplete. It should be remembered that constipation can cause bowel obstruction.

If none of the rectal laxatives above prove adequate to remove impacted faeces, rectal irrigation with normal saline can be performed3. Manual evacuation should be used as a last resort when all other methods of bowel management have been shown to be ineffective.

Combination therapy:

Constipation is a known side effect of opioid analgesics and should be addressed before opioid therapy begins. As opioid-induced constipation can be severe and adversely impact quality of life and compliance with therapy, prophylaxis with laxatives is considered to be the best approach.

Concurrent management on initiation of opioids frequently includes recommending certain lifestyle or dietary adjustments and initiating a scheduled regimen of laxatives. Laxative and cathartic therapy may be needed throughout opioid therapy and beyond. Effective management requires a composite of strategies, including behavioral and lifestyle changes (diet, activity, and fluid intake, as appropriate).

However medications used to manage opioid-induced constipation, such as laxatives, do not address the underlying opioid receptor-mediated cause of constipation and are often ineffective.

reference:
www.choices-in-oic.co.uk