Alleviating Bowel-Backup in Opioid Induced Constipation

OIC PREVENTION AND TREATMENT STRATEGIES

What protocols are generally utilized in hospitals for the prevention of OIC? How effective are these strategies?

I think, up until now, we haven’t seen much success in preventing or treating OIC. A typical protocol included the use of laxatives, progressing to milk of magnesia and enemas. If these strategies weren’t successful, the patient would typically end up with an impacted bowel and need to be disimpacted. This painful and humiliating process can take up to four or five days. Those methods are still often used despite the availability of new opioid antagonists that are very effective in preventing and treating OIC.

Once a patient experiences OIC, what medical strategies and lifestyle changes can be implemented? How have newer treatments, such as the opioid receptor antagonist methylnaltrexone bromide, changed the landscape of OIC management?

One of the most effective treatments for OIC is the use of methylnaltrexone. Unlike a standard opioid antagonist, methylnaltrexone doesn’t act on the brain. The drug stays in the bowel, so patients using the drug won’t experience withdrawal or increased pain. The agent has been on the market for four years, but because initial studies on the drug were performed in hospice patients, many physicians still reserve it for use in that population.

But methylnaltrexone should be used in conjunction with other strategies, because constipation is multi-factorial. Many patients have risk factors for constipation before they begin taking opioids—the drugs just magnify an existing problem. These risk factors may be related to a poor diet, a lack of exercise or low fluid intake. Taking methylnaltrexone in these cases won’t solve problems by itself. The goal of methylnaltrexone is to create an opioid-naive bowel, but the patient may need to add dietary changes and other lifestyle changes to eliminate the constipation.

I believe that methylnaltrexone is very effective with regard to OIC, but it is underused or used too late. Most clinics, hospitals and office practices have not yet put methylnaltrexone as part of an early intervention in their protocols for managing OIC. In talking with a variety of health care providers, the three biggest failures that providers have treating OIC are:

• waiting too long to use an effective pharmacological intervention such as methylnaltrexone
• limiting methylnaltrexone’s use to hospital settings
• only giving a single dose of methylnaltrexone instead of using it on a regular proactive basis to manage ongoing OIC

The best way to manage OIC is to be proactive instead of reactive.

Are there patient populations in which methylnaltrexone cannot be used?

So far studies have only identified one group that should not use methylnaltrexone—individuals with mechanical bowel blockages, such as a tumor. In these patients, using methylnaltrexone carries a serious risk of bowel perforation.But other than that group, there have been very few problems with the drug. There are no drug interactions. It won’t make dementia or heart palpitations worse. It won’t cause renal dysfunction, although doctors might want to reduce the dose for patients with existing renal dysfunction. But overall, the vast majority of patients have no problem using this drug. Methylnaltrexone gives us a specific, targeted pharmacological method to effectively manage OIC in most patients.

REFERENCES

1. National Cancer Institute. Gastrointestinal Complications. Available at: http://www.cancer.gov/cancertopics/pdq/supportivecare/gastrointestinalcomplications/Patient/page2. Accessed on June 8, 2012.