Skip to content
Clinical Trials – home

Rare diseases

Investigational molecules

Locations

Our offerNewsroom

Not recruiting

Study on Tramadol's Effect on Opioid-Induced Bowel Dysfunction in Patients Using Opioids

Verified siteRegistered drugNo placebo
Clinical Trials Concierge

Prefer not to search? Our Concierge searches the trials for you.

What is this trial about?

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

This clinical trial is focused on studying a condition known as opioid-induced bowel dysfunction, which can occur when people use opioid medications. The study will explore how a medication called tramadol, which is a type of pain reliever, affects this condition. Participants in the study will receive either tramadol or a placebo, which looks like the medication but does not contain any active ingredients.

The purpose of the study is to understand tramadol's impact on the digestive system, specifically looking at how it affects the movement and function of the stomach and intestines. This includes examining how quickly food moves through the digestive tract, the patterns of movement in the intestines, and the volume and water content in the colon. The study will also assess any symptoms of constipation and other related digestive issues.

Participants will be involved in the study for a period of up to 10 days. During this time, various assessments will be conducted, including imaging tests like MRI to observe the digestive system. The study aims to provide valuable insights into how tramadol influences bowel function in individuals who have not previously used opioids extensively.

The research process

The trial runs in 6 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 assessed by a study-affiliated medical doctor to confirm that you are healthy and meet the study's criteria.

    You will be required to sign an informed consent form, indicating that you understand the study and agree to participate.

  2. Step 2

    Initial assessment

    You will undergo an initial assessment to ensure you meet all the inclusion criteria, such as being between 20 and 40 years of age, of Northern European descent, and opioid naïve.

    Your anxiety levels will be evaluated using the STAI score, which should be in the range of 20-37, indicating no or low anxiety.

  3. Step 3

    Medication administration

    You will receive the medication tramadol or a placebo tablet orally. The dosage, frequency, and duration of administration will be explained to you by the study team.

    The aim is to determine tramadol's ability to induce opioid-induced bowel dysfunction by exploring gastrointestinal transit, motility pattern, secretion, and colonic volume.

  4. Step 4

    Monitoring and assessments

    Throughout the study, you will be monitored for changes in gastrointestinal transit time, both total and colorectal.

    You will be asked to provide subjective assessments of constipation and opiate withdrawal using specific questionnaires like PAC-SYM, BSFS, GSRS, BFI, and SOWS.

  5. Step 5

    Imaging and diagnostic tests

    You will undergo imaging tests such as MRI to assess colon volume, water content, gastric half emptying time, gastric accommodation, gastric motility, small bowel motility, and small bowel water content.

    These tests will help evaluate segmental transit time of the stomach, small intestine, and colonic segments.

  6. Step 6

    Completion of the study

    Upon completion of the study, you will have a final assessment to evaluate any changes or effects experienced during the trial.

    The study team will provide you with any necessary follow-up instructions or information.

Who can join the trial?

9 criteria

  • Must be healthy, as determined by a doctor involved in the study.
  • Must have signed an informed consent, which means you agree to participate after understanding the study details.
  • Must be able to read and understand the Danish language.
  • Must be male to avoid the influence of menstrual cycles on the study results.
  • Must be of Northern European descent to reduce differences in how the body processes the drug.
  • The researcher must believe that you understand the study details, will follow the study rules, and are likely to complete the study.
  • Must be opioid naïve, meaning you have not taken prescription opioids for at least one week, and it has been at least a year since you participated in any previous opioid study.
  • Must be between 20 and 40 years of age.
  • Must have a STAI score between 20 and 37, which means you have no or low anxiety at the start of the study. STAI is a questionnaire that measures anxiety levels.

Who cannot join the trial?

2 criteria

  • Patients who are not male cannot participate in the study.
  • Patients who are part of a vulnerable population cannot participate. A vulnerable population includes groups like children, pregnant women, or people who cannot make decisions for themselves.
Clinical Trials Concierge

Prefer not to search? Our Concierge searches the trials for you.

Tell us about your condition – we search every trial in Europe and connect you with the right site.

We usually reply within a few days

Verified sites

All sites with verified contact details – recruitment status may not be available; ask directly

  • Verified

    Mech Sense

    DenmarkAalborg, Denmark

Trial locations

Where you can join this trial

Countries are shaded by recruitment status. Click a recruiting country to ask about joining there.

Not recruiting
Not finding your country?

Not sure what to do next?

Joining a clinical trial can seem overwhelming. We guide you step by step, so you know exactly what to expect and how we support you through the process.

See the full process and FAQ

Investigated drugs

Tramadol is a medication used to relieve moderate to moderately severe pain. In this clinical trial, it is being studied to see how it affects bowel function, particularly when it is used alongside other opioid medications. Opioids can sometimes cause bowel problems, like constipation, and this study is looking at whether tramadol can influence these effects. The researchers are examining how tramadol affects the movement of the digestive system, the pattern of muscle contractions in the intestines, the amount of fluid secreted in the gut, and the size of the colon. This information will help understand if tramadol changes how the bowel works when opioids are used.

What is already known about the treatment

Tramadol – Tramadol is administered orally in the form of tablets or capsules. It is currently being studied for its effects on opioid-induced bowel dysfunction, a condition where bowel movements are disrupted due to opioid use. The main therapeutic indication for tramadol in this context is to assess its potential to cause or influence bowel dysfunction when used as a pain reliever. At the molecular level, tramadol works by binding to certain receptors in the brain and nervous system, altering the way the body perceives pain. It is classified pharmacologically as an opioid analgesic, which means it is a type of medication used to relieve moderate to severe pain.

Investigated diseases

Opioid-Induced Bowel Dysfunction – Opioid-induced bowel dysfunction is a condition that arises from the use of opioid medications, which can affect the normal functioning of the gastrointestinal tract. This condition is characterized by a range of symptoms, including reduced bowel movements, hard stools, and a sensation of incomplete evacuation. The opioids slow down the movement of the intestines, leading to increased water absorption and resulting in constipation. Over time, this can lead to discomfort, bloating, and abdominal pain. The dysfunction can also affect the motility patterns of the stomach and small intestine, altering the normal digestive process. Additionally, it may impact the secretion and volume of the colon, further complicating bowel movements.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2022-500108-23-00Estimated enrolment20 patientsSponsorAalborg University Hospital

sourced from the EU Clinical Trials Register and site verification

Want to learn more about this trial or check if you can participate?

Clinical Trials Concierge

Prefer not to search? Our Concierge searches the trials for you.

Tell us about your condition – we search every trial in Europe and connect you with the right site.

ClinicalTrials.eu

Every clinical trial in Europe, in plain language.

Explore the full ecosystem of clinical research in Europe.

Search trials

Legal notice · Published by CTIN POLAND sp. z o.o., ul. rtm. Witolda Pileckiego 67/109, 02-781 Warsaw, Poland · KRS 0001111334 · REGON 528919042 · NIP 9512598637

© 2026 Clinical Trials EU – European Clinical Trials Information Network

GDPR compliance, ISO 9001 and ISO 27001 certified (LL-C Certification)

On this site, “treatment” means an investigational medicine being studied in a clinical trial. Its safety and efficacy for the use being studied have not yet been confirmed, some participants may receive a placebo or a comparator medicine, and taking part does not guarantee any health benefit. The decision to take part is made by the doctor at the research site. This site is for information only and does not replace medical advice.

This service is not affiliated with the European Commission, the EMA, or the official CTIS system. Most information comes from publicly available international clinical-trial registries, supplemented by data from academic sites, national regulators and commercial sponsors. On this site, “treatment” and “therapy” mean a medicine being tested in a clinical trial. Its safety and effectiveness in the use being studied are not yet confirmed, some participants may receive a placebo or a comparator, and taking part does not guarantee a health benefit. The doctor at the research site decides who can take part. This site provides information, not medical advice. Certain content and visual elements on this website have been generated or enhanced using artificial intelligence (AI).