New Rx May Relieve Constipation Caused by Painkillers

Naloxegol eased constipation in opioid users and had few side effects

(RxWiki News) Many people deal with constipation at some point in their lives, but for people on particularly strong medications for pain, constipation can be a chronic complaint. One investigational medication may provide relief.

That medication, called naloxegol, is currently under review by the US Food and Drug Administration (FDA) as a treatment for constipation in people taking opioids (narcotic painkillers).

Researchers recently found that naloxegol relieved constipation more effectively than placebo (fake medication). Naloxegol also had few side effects.

"Ask your pharmacist about treatments to relieve constipation."

Naloxegol has just been tested in studies led by William Chey, MD, of the University of Michigan in Ann Arbor.

About half of people who take opioids for non-cancerous chronic pain develop constipation. That’s because while opioids bind to receptors in the brain, blocking the ability to feel pain, they also bind to receptors in the bowel, blocking the ability to evacuate the bowel. Naloxegol preserves the blockage in the brain but breaks down the gastrointestinal effects, allowing people to more effectively have bowel movements.

The researchers enrolled individuals, aged 18 to 84 years, who were taking 30 to 1,000 milligrams of morphine (or a similar medication) daily for at least four weeks and who had constipation. Constipation was defined as fewer than three spontaneous bowel movements a week, and one or more of the following symptoms: hard or lumpy stools, straining and the feeling that the bowel had not completely emptied.

Participants were taking opioids for back pain, arthritis, joint pain, fibromyalgia, headache, migraine, neuralgia or other conditions causing pain. No patients with cancer were in these studies.

There were 652 people in one study and 700 people in another. In each study, some people received naloxegol and others received placebo once a day for 12 weeks. No participants knew if they were on the medication or not. In both trials, individuals on naloxegol received either 12.5 or 25 milligrams daily.

Individuals kept logs of how often they had spontaneous bowel movements and if there were any problems they experienced. Any patient who failed to have a bowel movement in 72 hours was allowed to take bisacodyl (a stimulant laxative for short-term use) and then an enema if the bisacodyl did not work.

The researchers hoped naloxegol would allow participants to have three or more spontaneous bowel movements per week, with one or more extra bowel movements for at least nine of the 12 weeks. These researchers also wanted those on naloxegol to have that additional bowel movement in at least three of the final four weeks of the study.

In both studies, 25 milligrams of naloxegol worked better, by 10 percent to 15 percent, than placebo. In one of the two studies, patients on 12.5 milligrams of naloxegol fared better than those on placebo.

The side effects reported by those taking naloxegol were nausea, abdominal pain, vomiting, diarrhea and flatulence (having gas). These side effects were more evident in those taking the higher dose of naloxegol.

The authors of this study concluded that naloxegol may prove to be beneficial for people taking opioids who have tried other laxatives without much success.

“Providing a non-laxative medication that will block the constipating effects of opiates will fill a much needed gap in the treatment of constipation," said Steve Leuck, PharmD, a pharmacist in Santa Cruz, California and founder of AudibleRx, which provides internet-based, medication-specific counseling sessions in digital/audio format.

"I was especially encouraged to read that naloxegol proved beneficial in patients who had persistent constipation, even after using available treatments such as osmotic and stimulant laxatives," Dr. Leuck told dailyRx News. "Based on the study results, naloxegol appears to be reasonably low in side effects; however, being a new treatment option, its initial cost may limit its availability to the general population.”

This study appeared in The New England Journal of Medicine on June 4. It was supported by AstraZeneca, producer of naloxegol. Three of the study authors are also employees of AstraZeneca.

Review Date: 
June 6, 2014