Relistor: Relieving the constipation caused by opioids

Patients who experience severe pain may be prescribed opioids, but opioids can cause severe constipation in some people. These patients may stop taking the opioid because the constipation causes so much discomfort, but then their pain returns.

Relistor, also known as methylnaltrexone bromide, can help patients with this problem.

Opioid drugs are effective in relieving pain, but they can cause constipation too. This is because they work by binding to opioid receptors in both the central nervous system and the gut.

Development and use

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People who take opioids for pain may experience severe constipation.

In 1978, colleagues at the University of Chicago started looking for ways to help patients who would not take morphine for pain, because it would cause unbearable constipation.

They wanted to find a medication to treat the constipation, without reducing the painkilling effects of the opioid.

The opioid would need to target the receptors associated with pain relief but without causing the side effects.

The lead researcher, Dr. Goldberg, noticed that medications were already available that acted on the opioid receptors of the digestive system, without crossing into the brain, such as loperamide.

The team started screening compounds, in the search for a drug that would relieve constipation without entering the brain and neutralizing morphine’s painkilling effects.

A compound called N-methyl-naltrexone (MNTX), created by Boerhringer Ingelheim, a German pharmaceutical company, looked promising.

In 2005, following a number of tests, two pharmaceutical companies signed an agreement to develop the drug and commercialize methylnaltrexone.

The new drug would be used to treat opioid-induced side effects, including constipation and post-operative ileus. In this condition, a part of the intestine becomes paralyzed, so that food and drink cannot be pushed forward. Post-operative ileus can happen after abdominal surgery.

Relistor was approved for the treatment of opioid-induced constipation in 2008 by the United States Food and Drug Administration (FDA).

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How Relistor works

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