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Methoxyflurane Compared to Morphine for Pain Relief in Patients with Acute Myocardial Infarction Before Hospital Admission

Verified siteRegistered drugNo placebo
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What is this trial about?

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

This study involves patients experiencing Acute Myocardial Infarction, which is a serious condition that occurs when blood flow to a part of the heart muscle becomes blocked, causing chest pain. The study will compare two different pain-relieving medications used before patients reach the hospital. One medication is methoxyflurane, which is given as a vapor that patients breathe in themselves through an inhaler device. The other medication is morphine, which is given through a vein as an injection. The main purpose of this study is to find out if methoxyflurane is at least as effective as morphine in reducing chest pain in patients with this heart condition.

During the study, patients will receive one of the two pain medications when emergency medical services arrive to help them. The medication will be given to patients who have moderate to severe chest pain. Throughout the treatment, medical staff will measure how much the pain decreases and how quickly the pain relief occurs. They will use a pain scale where patients rate their pain from zero to ten, with higher numbers meaning more pain. The goal is to bring the pain level down to three or below.

The medical team will also monitor several other aspects during and after treatment. They will check how long it takes for the pain to reduce by half and how long it takes to reach low pain levels. They will measure heart rate, blood pressure, oxygen levels in the blood, and heart electrical activity when patients arrive at the hospital. The study will also track any unwanted effects from the medications, such as slow breathing, excessive sleepiness or agitation, dizziness, itching, nausea, vomiting, or headache. Each patient will receive treatment for one day as part of their emergency care.

The research process

The trial runs in 5 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial treatment administration

    Upon joining the study, your condition will be assessed. You will have chest pain related to a heart attack (acute myocardial infarction) that has been present for less than 12 hours, with moderate to severe pain intensity.

    Your pain level will be measured using a visual scale where you indicate how much pain you feel from 0 (no pain) to 10 (worst pain imaginable). Your initial pain score will be greater than 6 out of 10.

    You will be randomly assigned to receive one of two pain relief treatments: either methoxyflurane (a liquid that you inhale as vapor) or morphine (given through a vein).

    If you receive methoxyflurane, you will self-administer it by inhaling the vapor from a device. The product contains 99.9% methoxyflurane in a 3 mL liquid form.

    If you receive morphine, it will be administered directly into your vein as a bolus injection (a single dose given at once).

  2. Step 2

    Monitoring during treatment

    Your pain level will be regularly assessed throughout the treatment period using the same visual scale.

    The time it takes for your pain to decrease will be recorded, specifically noting when your pain score reaches 3 or below on the scale.

    The time required for your pain to reduce to half of its initial level will also be measured.

    Your vital signs will be monitored, including heart rate (how fast your heart beats), blood pressure (the pressure of blood in your arteries), and oxygen levels in your blood.

    An electrocardiogram (a test that records the electrical activity of your heart) will be performed to monitor any changes.

  3. Step 3

    Assessment at 30 minutes

    At 30 minutes after treatment begins, your pain level will be specifically evaluated to determine if it has decreased to 3 or below on the visual scale.

    This measurement is the main indicator used to assess how well the treatment is working for you.

  4. Step 4

    Safety monitoring

    Throughout the treatment, you will be monitored for any side effects or complications.

    Your breathing rate will be checked to ensure it does not drop below 10 breaths per minute.

    Your level of alertness and sedation will be assessed using a specific scale to ensure you are not overly sedated or agitated.

    You will be observed for potential side effects including dizziness, itching, nausea, vomiting, and headache.

  5. Step 5

    Final assessment upon hospital arrival

    When you arrive at the hospital, a final assessment of your vital signs will be conducted.

    This will include measurements of your heart rate, blood pressure, oxygen levels, and an electrocardiogram.

    All information collected during your participation will be recorded for analysis.

Who can join the trial?

5 criteria

  • You must be 18 years of age or older
  • You must be receiving care before arriving at the hospital for a ST elevation myocardial infarction, which is a type of heart attack where a major blood vessel in the heart is completely blocked
  • You must have chest pain that started less than 12 hours ago
  • Your chest pain must be moderate to severe, meaning a pain score greater than 6 out of 10 on a scale where 0 is no pain and 10 is the worst pain imaginable
  • Your ECG, which is a test that records the electrical activity of your heart, must show signs of a ST elevation myocardial infarction according to medical guidelines from 2017

Who cannot join the trial?

4 criteria

  • The study does not list specific reasons why patients cannot participate
  • However, patients should be aware that the study involves treatment for acute myocardial infarction, which is a heart attack that happens when blood flow to part of the heart muscle is blocked
  • The study compares two pain relief medications: methoxyflurane, which is a medication the patient breathes in themselves to reduce pain, and morphine, which is a strong pain medication
  • This study is designed for adults and elderly patients experiencing chest pain related to a heart attack
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Investigated drugs

  • Methoxyflurane

    is a pain-relieving medication that the patient breathes in by themselves. In this trial, it is being tested to see if it works as well as morphine for reducing chest pain in people who are having a heart attack before they get to the hospital.

  • Morphine

    is a strong pain-relieving medication that is commonly used to treat severe pain, including chest pain during a heart attack. In this trial, it is being compared to methoxyflurane to see which medication works better for pain relief in emergency situations.

What is already known about the treatment

  • Methoxyflurane

    Methoxyflurane is an inhaled pain relief medication that comes in a portable inhaler device, allowing patients to breathe in the medicine themselves when they need it. Currently, it is used in emergency medical situations for quick pain relief, and this clinical trial is testing whether it works as well as morphine for chest pain caused by heart attacks. The medication works by being absorbed through the lungs into the bloodstream, where it affects pain receptors in the brain and nervous system to reduce the feeling of pain. It belongs to a class of drugs called inhalational analgesics, which are pain relievers that are breathed in rather than swallowed or injected.

  • Morphine

    Morphine is a strong pain relief medication that is typically given by injection into a vein or muscle, especially in emergency situations like heart attacks. It is a well-established and widely used medication in medical practice for treating severe pain, including chest pain from heart attacks. Morphine works by attaching to specific receptors in the brain and spinal cord called opioid receptors, which blocks pain signals and changes how the body feels and responds to pain. This medication belongs to the pharmacological class known as opioid analgesics, which are among the most powerful pain relievers available in medicine.

Investigated diseases

Acute Myocardial Infarction – This is a condition commonly known as a heart attack that occurs when blood flow to a part of the heart muscle becomes blocked. The blockage is usually caused by a blood clot that forms in a coronary artery, which supplies oxygen-rich blood to the heart. When the heart muscle does not receive enough oxygen, the affected tissue begins to die. Patients typically experience severe chest pain or discomfort that may spread to the arms, neck, jaw, or back. The condition develops suddenly and requires immediate medical attention. Without prompt restoration of blood flow, the damage to the heart muscle becomes permanent and can affect the heart's ability to pump blood effectively.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2025-523349-86-00Protocol codeAPHP 180610Estimated enrolment700 patientsSponsorAssistance Publique Hopitaux De Paris

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