A once-daily tablet for opioid-induced constipation
Naloxegol
A once-daily tablet for opioid-induced constipation that blocks opioids in the gut without reducing pain relief.
What is Naloxegol?
Naloxegol is a once-daily tablet used to treat opioid-induced constipation, the constipation caused by strong painkillers known as opioids. It is a peripherally-acting opioid blocker, meaning it blocks opioids in the gut to relieve constipation while leaving the pain relief from the brain largely untouched. It is best taken on an empty stomach, in the morning, before the first meal of the day. It must not be taken with strong medicines or grapefruit that affect how the body handles it. The most common side effect is tummy pain, and a rare but serious risk is a tear in the bowel wall.
Education and reference only. This is a plain-language guide to Naloxegol — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Naloxegol is a medicine used to treat opioid-induced constipation, a common problem in people taking strong painkillers called opioids. Opioids relieve pain in the brain but also slow the bowel, causing constipation that everyday laxatives may not fully relieve. Naloxegol is a peripherally-acting opioid blocker, which means it acts mainly in the gut to undo the bowel-slowing effect of opioids without affecting the pain relief. It is taken by mouth as a once-daily tablet, usually when laxatives alone have not worked well enough, and it works best when taken on an empty stomach.
How it works
Opioid painkillers act on opioid receptors around the body; in the gut they slow movement and harden the stool. Naloxegol blocks these receptors in the gut wall so the bowel can move more normally, while being designed not to enter the brain to any meaningful degree, so it does not reduce pain relief. Because food increases how much is absorbed, it is taken on an empty stomach for a steady effect. It works on the cause of opioid-induced constipation, so it is taken every day while opioid treatment continues.
Company & origin
Originated / developed by: Specialist manufacturer.
A medicine used in the UK to treat constipation caused by strong painkillers, taken as a once-daily tablet on an empty stomach.
Practical use
How to take Naloxegol
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take one tablet by mouth once a day on an empty stomach, usually in the morning before your first meal.
- Leave time after the tablet before eating, and avoid grapefruit and grapefruit juice while taking it.
- Stop it and seek urgent help if you get severe, sudden or worsening tummy pain, as this can signal a bowel tear.
- Tell your team about all your medicines, as some strong medicines must not be taken with naloxegol.
- Tell your prescriber if you get sweating, cramps or a fast heartbeat, as these can be withdrawal-type symptoms.
Weighing it up
Advantages & disadvantages of Naloxegol
Advantages
- Relieves opioid-induced constipation by acting on its cause in the gut.
- Does not reduce the pain relief from opioids, as it works mainly outside the brain.
- A simple once-daily tablet for people whose laxatives have not worked well enough.
Disadvantages
- Must be taken on an empty stomach and kept apart from grapefruit, which takes planning.
- Cannot be taken with certain strong medicines that change how the body handles it.
- Commonly causes tummy pain, and carries a rare but serious risk of a bowel tear.
Practical use
Good to know
The most important practical point with naloxegol is how to take it: on an empty stomach, usually first thing in the morning, at least half an hour before the first food of the day, because food increases its absorption. A crucial safety point is that it must not be taken with strong medicines that block the liver enzyme that breaks it down, nor with grapefruit or grapefruit juice, because these can raise its levels too much. The most common side effect is tummy pain, along with diarrhoea, nausea and wind. A rare but serious risk is a tear (perforation) in the bowel wall, so severe, sudden or worsening tummy pain needs urgent medical attention. Like similar medicines, it can cause opioid-withdrawal-type symptoms, and it must not be used if there is, or might be, a blockage in the gut.
Who should not take it / use with caution
- People who have, or are suspected to have, a blockage in the gut must not take it.
- People taking certain strong medicines that block its breakdown should not take it together.
- People who have had a serious allergic reaction to naloxegol should not take it, and it is used with caution in pregnancy under specialist advice.
Monitoring
- Reviewing how well the constipation improves and whether the dose suits you.
- Watching for severe tummy pain that could signal a bowel tear.
- Reviewing other medicines for interactions, particularly strong enzyme-blocking medicines.
Side effects
- Tummy pain, which is the most common effect, along with diarrhoea, nausea and wind.
- Opioid-withdrawal-type symptoms such as sweating, cramps or a fast heartbeat in some people.
- Rarely but seriously, a tear in the bowel wall, which needs urgent medical attention.
Key interactions
- Strong medicines that block the liver enzyme breaking down naloxegol must not be taken with it.
- Grapefruit and grapefruit juice can raise its levels, so they are avoided.
- Using it with other opioid-blocking medicines is not recommended, as effects can add up.
Available as: Tablets taken by mouth.
Answers
Naloxegol: frequently asked questions
What is naloxegol used for?
It is used to treat constipation caused by strong opioid painkillers, by blocking the effect of opioids in the gut so the bowel can move more normally.
Why must I take it on an empty stomach?
Food increases how much naloxegol is absorbed, so it is taken on an empty stomach, usually in the morning before your first meal, for a steady effect.
Why should I avoid grapefruit?
Grapefruit and grapefruit juice can raise the level of naloxegol in the body too much, so they are avoided while you take it.
Does it stop my pain relief working?
No. It works mainly in the gut and not the brain, so it relieves the constipation without reducing the pain relief from your opioid.
When should I seek urgent help?
Stop the tablet and get urgent medical help if you have severe, sudden or worsening tummy pain, as this can rarely signal a tear in the bowel.
The wider class
About Peripherally-acting opioid blocker for constipation (PAMORA)
Naloxegol belongs to the peripherally-acting opioid blocker for constipation (pamora) class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
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Authoritative sources
- BNF
- NICE CKS
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