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Study on the Effects of Naloxegol and Codeine on Opioid-Induced Constipation in Healthy Volunteers

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What is this trial about?

A plain-language summary of the goals, design and what participants do

This clinical trial is focused on studying the effects of certain medications on opioid-induced constipation, a condition that can occur when using opioid pain medications. The study will evaluate the effects of naloxegol, a medication that helps relieve constipation caused by opioids, and codeine, an opioid pain medication. Additionally, bisacodyl, a laxative, will be used during the study to help understand its effects on bowel movements.

The purpose of the study is to better understand how naloxegol works in healthy individuals. Participants will take part in a series of study visits where they will receive different combinations of the medications, including a placebo. The study will use MRI (Magnetic Resonance Imaging), a type of scan that creates detailed images of the inside of the body, to observe changes in the movement and size of the intestines after taking the medications and eating a meal.

Throughout the study, participants will be given different combinations of the medications, such as naloxegol with codeine, placebo with codeine, and placebo with placebo. The effects on the intestines will be observed at different times, including after eating an oat porridge meal and after taking bisacodyl. This study aims to provide insights into how these medications affect the digestive system, particularly in relation to constipation caused by opioids.

The research process

The trial runs in 7 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Joining the study

    Upon joining the study, you will be informed about the trial's purpose and procedures. You will be asked to provide written consent to participate.

    You will be required to use highly effective methods of birth control during the trial period.

  2. Step 2

    Initial assessment

    An initial assessment will be conducted to ensure you meet the eligibility criteria, including age, body mass index (BMI), and stool pattern.

    You must not have used any opioid medication 14 days prior to the start of the trial.

  3. Step 3

    First study visit

    During the first study visit, you will receive a lactose monohydrate 320mg tablet to be taken orally.

    This medication will be administered once during this visit.

  4. Step 4

    Second study visit

    At the second study visit, you will again receive a lactose monohydrate 320mg tablet to be taken orally.

    This is the final administration of this medication.

  5. Step 5

    Third study visit

    During the third study visit, you will be given sirupus simplex 30mL, followed by an additional 15mL after two hours.

    This administration occurs only once during the study.

  6. Step 6

    Medication administration

    Throughout the study, you may receive different combinations of medications, including naloxegol and codeine, or a placebo.

    The medications will be administered orally, and the effects on gastrointestinal motility and volumes will be monitored.

  7. Step 7

    Final assessment

    At the end of the study, a final assessment will be conducted to evaluate the effects of the medications on your gastrointestinal system.

    This will include monitoring colonic motility and segmental colorectal volumes.

Who can join the trial?

7 criteria

  • The participant must provide voluntary written consent to join the study, or their legally authorized representative must do so on their behalf.
  • The participant must use highly effective birth control methods. These are methods that have a very low chance of failure (less than 1% per year) when used correctly. Examples include implants, injections, combined oral contraceptives, certain intrauterine devices (IUDs), complete sexual abstinence (not having heterosexual intercourse during the study), or having a partner who has had a vasectomy.
  • The participant must be a man or woman aged between 18 and 65 years old.
  • The participant must have a Body Mass Index (BMI) between 18 and 25. BMI is a measure of body fat based on height and weight.
  • The participant must have a normal stool pattern, which means having between 3 bowel movements per day and 3 per week. The stool should not be very hard or very loose in more than 25% of bowel movements.
  • The participant must not have used any opioid medication for at least 14 days before starting the study. Opioids are a type of pain medication.
  • The participant can take medications for allergies, chronic medical conditions, and migraine headaches during the study, except for opioids used for acute migraine treatment. If the participant is taking medication for chronic migraines or preventive therapy, they must have been on a stable dose for at least 1 month before the study. Participants on stable doses of antidepressants for at least 3 months before the study can also participate.

Who cannot join the trial?

9 criteria

  • Patients who are not healthy volunteers cannot participate.
  • Patients who are under 18 years old cannot participate.
  • Patients who are pregnant or breastfeeding cannot participate.
  • Patients with a history of allergic reactions to the study medication cannot participate.
  • Patients who are currently taking medications that might interfere with the study cannot participate.
  • Patients with any significant medical conditions that might affect the study results cannot participate.
  • Patients who have participated in another clinical trial recently cannot participate.
  • Patients who have a history of drug or alcohol abuse cannot participate.
  • Patients who are unable to comply with the study procedures cannot participate.
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Investigated drugs

  • Naloxegol

    is a medication used to help relieve constipation caused by opioid pain medications. It works by blocking the effects of opioids in the gut, which helps to restore normal bowel movements. In this clinical trial, naloxegol is being studied to understand how it affects the movement and volume of the gastrointestinal tract in healthy volunteers.

  • Codeine

    is a medication commonly used to treat mild to moderate pain. It works by changing the way the brain and nervous system respond to pain. In this study, codeine is being used to see how it affects the gastrointestinal system, particularly in terms of motility and volume, when compared to naloxegol.

What is already known about the treatment

Naloxegol – Naloxegol is taken orally in the form of a tablet and is used to treat opioid-induced constipation, a common side effect of opioid pain medications. It works by blocking the effects of opioids in the gut without affecting pain relief in the brain, helping to restore normal bowel function. Naloxegol is classified as a peripherally acting mu-opioid receptor antagonist, meaning it specifically targets receptors in the digestive tract to alleviate constipation. Currently, it is being studied to better understand its effects on gastrointestinal motility and volumes in healthy individuals.

Investigated diseases

Opioid-induced constipation – Opioid-induced constipation is a condition that occurs when opioid medications, commonly used for pain relief, slow down the movement of the digestive tract. This slowing effect leads to infrequent bowel movements, difficulty passing stools, and hard or lumpy stools. The condition develops as opioids bind to receptors in the gut, reducing gastrointestinal motility and increasing fluid absorption from the intestines. Over time, this can result in discomfort, bloating, and abdominal pain. The severity of symptoms can vary depending on the type and dosage of opioid medication used. Regular bowel movements may become challenging, requiring adjustments in diet or lifestyle to manage symptoms.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2024-512673-28-00Estimated enrolment15 patientsSponsorUZ Leuven

sourced from the EU Clinical Trials Register and site verification

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