Patients with advanced cancers who took methylnaltrexone (Relistor), a drug indicated for the relief of opioid-induced constipation, lived longer and had fewer reports of tumor progression than patients with cancer who did not receive the drug, according to study results presented at the ANESTHESIOLOGY 2015 Annual Meeting.1

The retrospective survival analysis included 229 patients who had participated in 2 randomized, controlled clinical trials focused on constipation relief in patients receiving palliative care for various late-stage cancers and other terminal diseases. None of the patients enrolled responded to conventional laxatives.

Participants were randomly assigned to receive methylnaltrexone for opioid-induced constipation (117 patients) or placebo (112 patients).

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Constipation relief was experienced by 57% of patients who received methylnaltrexone; the remaining patients who received the drug did not experience constipation relief.

In addition, those who responded to methylnaltrexone lived twice as long as those who did not respond or had received the placebo. Reports of tumor progression were also significantly fewer in patients who responded to methylnaltrexone (7.6%) compared with those who did not respond (22%) or who took the placebo (25.4%).

In a separate analysis, the researchers reviewed the effects of methylnaltrexone on another 135 patients from the same analysis who had advanced illnesses other than cancer, such as congestive heart failure, advanced chronic obstructive pulmonary disease, or neurologic diseases.

More than half of the patients experienced constipation relief with methylnaltrexone; however, no additional survival was achieved, even for those who responded to the drug’s digestive effects.

These results indicate that improved bowel function is not likely to be the only explanation for improved survival in patients with cancer and suggests methylnaltrexone could have a role in cancer therapy, reported study co-author Filip Janku, MD, PhD, assistant professor of investigational cancer therapeutics at the University of Texas MD Anderson Cancer Center in Houston, TX.

Methylnaltrexone, a version of naltrexone that does not cross the protective barrier that surrounds the brain, blocks morphine’s effects on the bowels, where it causes painful constipation, but does not interfere with its beneficial effect on pain

Jonathan Moss, MD, PhD, lead author of this study and professor of anesthesia and critical care, and colleague Patrick Singleton, PhD, assistant professor of medicine, both at The University of Chicago, found in a previous study that cells from various human cancers have significantly more opioid receptors than noncancerous cells.

“We also found that methylnaltrexone reduced tumor growth and spread in several cancer models,” Dr. Singleton said. “Some of our findings with methylnaltrexone occurred without opioids, suggesting that the opioid receptor and its pathway may be a therapeutic target for cancer treatment.”


1. University of Chicago Medical Center. Drug for digestive problem can extend survival for many advanced cancer patients [press release]. EurekAlert! Web site. Accessed October 29, 2015.