Why Does Fentanyl Cause Itching?

There are illicit opioids sold on black markets, such as heroin, but many opioids are prescription drugs that are administered in medical settings. Fentanyl is one of the most powerful prescription opioids, and it’s also unfortunately highly misused in the United States.

Fentanyl is intended for the treatment of breakthrough pain in cancer patients who are already receiving around-the-clock opioid-based pain management treatment, but it’s both misunderstood by doctors prescribing it and by the people who use it.

• Nausea
• Vomiting
• Drowsiness
• Vertigo
• Dizziness
• Constipation
• Sweating
• Fatigue
• Palpitations
• Abdominal pain
• Dry mouth
• Malaise
• Weakness
• Swelling of arms and legs
• Muscle spasms
• Depression
• Rash

With so many potential symptoms, people may have very different experiences with fentanyl use. A wide range of factors determines how a particular person reacts to particular drugs. So, what is it that causes someone to experience itchiness when they take opioids like fentanyl?

Until recently, doctors and researchers believed opioid-related itching was because of how the drugs interact with the user’s nervous system. There are brain receptors that respond to opioids and most opioid painkillers are nonspecific. Nonspecific opioids bind to all of these receptors, which is why they’re so effective in dealing with pain.

In research recently published by UNC School of Medicine in the Nature Chemical Biology Journal, it was shown that a specific receptor protein, MRGRPX2, can lead to an immune system response that then creates the itching that comes along with the use of opioids like fentanyl.

Kate Lansu, who co-authored the paper, said that receptors in mast cells, which are part of the immune system, respond to an activation signal when opioids are taken. This response leads to the release of histamine and other inflammatory agents. The process has a specific name: degranulation.

Lansu said that when this process occurs, other cells go to the site of inflammation to clear what they sense to be an infection, similar to what happens when someone has an allergic response.

The hope is that by studying the specifics of why fentanyl causes itching as well as looking at why other commonly used opioids cause itching, researchers will be able to develop an antagonist for this particular receptor, which would ultimately relieve the side effect of itching.

So, to answer the question of why fentanyl causes itching: it’s because when the opioid drug binds to certain receptors in your brain and body, it triggers a response not unlike an allergic response.

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