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Study of safe and effective postoperative opioid dosing with morphine hydrochloride and oxycodone hydrochloride in patients with chronic opioid use

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What is this trial about?

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

The study focuses on people who have opioid dependent chronic pain and are scheduled for major surgery. It evaluates two strong pain medicines that are given directly into a vein: oxycodone and morphine. The purpose is to identify the safest method for giving extra pain relief after the operation.

After surgery, participants receive the study medication through an IV while they stay in the recovery area known as the post‑anesthesia care unit. Their blood‑oxygen level (SpO2) is continuously checked, and pain intensity is recorded using a Numeric Rating Scale that runs from 0 (no pain) to 10 (worst pain). The observation period covers the first 24 hours after surgery, during which the number of doses given, any episodes of low oxygen, the need for supplemental oxygen, breathing rate, nausea, vomiting, and overall comfort are monitored.

The research process

The trial runs in 9 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Enrollment and randomization

    After providing informed consent, the patient is entered into the study and assigned by chance to receive one of two intravenous opioid medications.

    The assignment determines whether the patient will receive oxycodone solution or morphine solution during the postoperative period.

  2. Step 2

    Surgery and transfer to recovery

    The patient undergoes a major surgical procedure under general anesthesia.

    Immediately after surgery, the patient is moved to the post‑anesthesia care unit (PACU), a recovery area where vital signs are closely watched.

  3. Step 3

    Initial postoperative monitoring

    In the PACU, continuous monitoring of heart rate, blood pressure, and oxygen saturation (SpO2) begins.

    Oxygen saturation is the percentage of oxygen in the blood; a value below 92 % for 60 seconds or longer is recorded as an important safety event.

  4. Step 4

    Administration of study medication

    The patient receives the assigned medication by intravenous infusion, meaning the drug is delivered directly into a vein.

    If assigned to the oxycodone group, the solution contains oxycodone hydrochloride at a total strength of 540 mg.

    If assigned to the morphine group, the solution contains morphine hydrochloride at a total strength of 720 mg.

    The medication is given only when needed for pain (prn), based on the patient’s pain rating, and may be repeated during the stay in the PACU and for the first 24 hours after surgery.

  5. Step 5

    Pain assessment

    Pain is measured using the Numeric Rating Scale (NRS), where 0 means no pain and 10 means the worst pain imaginable.

    The goal is to achieve a pain score lower than 3; the time required to reach this level is recorded.

  6. Step 6

    Recording of opioid use

    The total number of opioid doses given in the PACU is counted.

    The total number of doses given from the start of the study medication until 24 hours after surgery is also recorded.

  7. Step 7

    Monitoring for side effects

    The patient is observed for the need for supplemental oxygen to keep SpO2 above 94 %.

    Sedation level is evaluated with standard scores, and any episodes of nausea, vomiting, or slow breathing (respiratory rate less than 8 breaths per minute) are documented.

  8. Step 8

    Post‑operative follow‑up

    Vital signs and pain scores continue to be recorded for the first 24 hours after surgery.

    If the patient’s pain remains high (NRS greater than 7) after six consecutive doses, the patient may be withdrawn from the study.

  9. Step 9

    Completion of study participation

    Once 24 hours of postoperative data have been collected, the patient’s involvement in the trial ends.

    All recorded information is used to evaluate the safest and most effective opioid dosing strategy for patients with chronic opioid use.

Who can join the trial?

4 criteria

  • Be at least 18 years old.
  • Take a daily amount of opioids that is the same as or more than 30 mg of oral morphine equivalents (OMEQ) for at least 30 days before surgery. (Oral morphine equivalents is a way to compare the strength of different opioid medicines to the strength of morphine taken by mouth.)
  • Plan to have an elective abdominal or orthopedic surgery that is scheduled in advance and will require anesthesia lasting more than one hour. (Elective means the surgery is planned, not an emergency; anesthesia is the medicine that makes you sleep or not feel pain during the operation.)
  • Be able to understand and speak Danish or English well enough to read the study information, give permission to join, and tell the study team how much pain you feel using a simple rating scale (the NRS). (NRS stands for Numeric Rating Scale, where you rate pain from 0 = no pain to 10 = worst pain.)

Who cannot join the trial?

7 criteria

  • Anyone whose oxygen saturation (the amount of oxygen in the blood) is constantly lower than 92% before surgery and who is not receiving extra oxygen is not eligible.
  • People who are pregnant or are currently breastfeeding are excluded.
  • Individuals with moderate to severe kidney problems, defined as an estimated kidney filtration rate (eGFR—a test that measures how well the kidneys filter waste) below 60 ml/min, cannot participate.
  • Those who have significant memory or thinking problems, such as cognitive decline or dementia, that prevent them from understanding the study and giving consent are excluded.
  • Anyone with a known history of misusing illegal drugs or prescription medicines—including taking more of a prescribed medication than directed—is not allowed to join.
  • People who are currently taking medications that block opioid effects, known as opioid antagonists (for example, the partial blocker buprenorphine or the blocker naltrexone), are excluded.
  • Individuals who are currently being treated with methadone (a strong opioid medication) are not eligible.
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Investigated drugs

  • Oxycodone

    is given as a liquid that can be injected into a vein (IV infusion). In this study it is used to provide pain relief after major surgery for patients who already use opioids regularly. The researchers are testing how safely this medication can be given on an as‑needed basis, watching for any breathing problems such as low oxygen levels in the recovery room.

  • Morphine

    is also supplied as a liquid for injection into a vein (IV infusion). It serves the same purpose as oxycodone in the trial: to manage postoperative pain in people who are chronic opioid users. The study compares its safety when given as needed after surgery, with special attention to episodes of oxygen desaturation in the post‑anesthesia care unit.

What is already known about the treatment

  • Oxycodone

    Oxycodone hydrochloride is supplied as a sterile solution for injection or infusion, given through an IV line. It is an approved opioid pain medicine that is widely used and described in many medical references. It works by binding to opioid receptors in the brain and spinal cord, which reduces the feeling of pain. It belongs to the class of strong opioid analgesics.

  • Morphine

    Morphine hydrochloride is provided as a clear solution for injection, administered by IV infusion. It is a long‑standing opioid pain reliever that is well documented in medical literature. It relieves pain by attaching to opioid receptors in the central nervous system, lowering pain signals. It is classified as a potent opioid analgesic.

Investigated diseases

Opioid-dependent chronic pain - A long‑lasting pain condition in which the individual regularly uses opioid medications and has developed physiological dependence on them. Over time, the pain may become more widespread or intensify, leading to higher opioid doses to achieve relief. The body adapts to the drug, causing tolerance, so the same dose becomes less effective. As dependence deepens, withdrawal symptoms can appear when opioid use is reduced or stopped. This cycle can result in escalating pain perception and increased difficulty managing daily activities.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2026-526719-13-00Protocol codePOISONEstimated enrolment318 patientsSponsorRegion Hovedstaden

sourced from the EU Clinical Trials Register and site verification

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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.

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