A Pilot Study on the Use of Methoxyflurane (Penthrox®) for Pain Control in the Emergency Department

Patients commonly visit the emergency department (ED) for pain after musculoskeletal injury and need early treatment with analgesic. Prompt and adequate pain relief can reduce suffering and promote early discharge and return to work. Nonsteroidal anti-inflammatory drugs (NSAIDs) and opioids are the major injectable analgesic used for moderate to severe pain in EDs in Hong Kong. They are given via intravenous or intramuscular route for faster onset of action to achieve rapid pain relief in the emergency setting. However, injections are invasive and can be distressing for patients. Methoxyflurane (Penthrox®) is recently introduced to our emergency department as an inhalational analgesic. It has been granted registration approval in Hong Kong since 2018, but it is not widely used in the locality. Methoxyflurane is a volatile fluorinated hydrocarbon self-administrated by inhalation through a portable hand-held whistle-shaped inhaler device (Penthrox®) to relieve pain associated with trauma or minor surgical procedures in stable and conscious patients. In this study, the investigators will evaluate the efficacy and safety Penthrox® in the treatment of acute traumatic pain in hospital emergency department setting by comparing it to another conventional analgesic commonly used.

Study Overview

• Status: Completed
• Conditions: Acute Traumatic Pain
• Intervention / Treatment: Drug: Methoxyflurane; Drug: Ketorolac

• Study Type: Interventional
• Enrollment (Actual): 40
• Phase: Phase 3

Contacts and Locations

Study Locations

• Hong Kong
  • Hong Kong, Hong Kong
    • Hospital Authority

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 64 years (Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

Inclusion Criteria:

• Patients of both sexes from 18 to 64 years of age
• Presented to the ED in Ruttonjee Hospital for musculoskeletal injury within 72 hours of onset (Types of injury include contusion, sprain, crushing, burn, laceration, fracture and dislocation)
• Moderate pain at screening (10-point Numeric Rating Scale ≥4 to ≤7)

Exclusion Criteria:

• Critical or life-threatening condition requiring resuscitation
• Limb-threatening condition or any injuries requiring immediate management
• Hemodynamically unstable (systolic blood pressure <90 mmHg, diastolic blood pressure <60mmHg)
• Respiratory distress with respiratory rate >20 breath per minute or oxygen saturation <95% on room air
• Pregnant or breastfeeding women
• Impaired consciousness from any cause such as head injury and acute intoxication, based on the judgement of investigator
• Any physical, visual or cognitive conditions that may affect patient's ability to use visual analog scale for self-assessments of pain intensity
• Concomitant use of other analgesic within 5 hours (8 hours for diclofenac sodium) prior to presentation to ED
• Other pre-existing chronic pain condition
• Unable or refuse to provide written informed consent
• Unable to understand and converse in the language spoken

• Contraindication to inhalational methoxyflurane

  1. Known personal or family history of hypersensitivity to methoxyflurane or any fluorinated anesthetics
  2. Known pre-existing clinically significant renal or hepatic impairment
  3. Known personal or family history of malignant hyperthermia
  4. Concomitant use of nephrotoxic agents such as gentamicin, tetracycline, colistin, polymyxin B and amphotericin B
  5. Concomitant use of cytochrome P450 inducers such as alcohol, isoniazid, phenobarbital and rifampicin

• Contraindication to intramuscular ketorolac

  1. Known allergy to NSAIDS
  2. Known pre-existing clinically significant renal impairment or at risk for renal failure due to volume depletion
  3. Active major bleeding
  4. Suspected or confirmed cerebrovascular bleeding
  5. History of peptic ulcer disease, gastrointestinal bleeding or perforation
  6. Concomitant use of aspirin, other NSAIDS, anticoagulant or novel anticoagulant agent, pentoxifylline and probenecid
  7. Known bleeding disorders such as haemophilia, thrombocytopenia
  8. Heart failure
  9. Per-operative period of coronary artery bypass graft (CABG) surgery
  10. Concurrent asthmatic attack

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Inhalational methoxyflurane (Penthrox)	Drug: Methoxyflurane; Each patient in the methoxyflurane group will use one Penthrox inhaler under supervision of trained personnel. After priming the inhaler with 3 mL of methoxyflurane, patient is instructed to inhale through the mouthpiece to obtain analgesia, and then exhale back into the mouthpiece so that any unmetabolized methoxyflurane can be adsorbed by activated charcoal chamber. First few breaths should be gentle and then breathe normally through Inhaler. Onset of pain relief is rapid and occurs after 6-10 inhalations. If stronger analgesia is required, patient can cover the diluter hole with a finger during inhalation. Patients are able to titrate the amount of methoxyflurane inhaled and should be instructed to inhale intermittently to achieve adequate pain control.; Other Names: Penthrox
Active Comparator: Intramuscular ketorolac	Drug: Ketorolac; Each patient in the ketorolac group will receive one dose of 30mg intramuscular ketorolac injected at gluteal muscle by nursing staff as usual daily practice.; Other Names: Toradol

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
The change in pain intensity over 60 mins in terms of 100-mm VAS	Patients are instructed to complete a questionnaire with visual analogue scale (VAS), a 100-mm horizontal straight line whereas"0" at the left end indicates "no pain at all" and "10" at the right end indicates "the worst possible pain I can imagine".	Measure at baseline and at 5, 15, 30 and 60 minutes after drug administration

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Blood pressure	Blood pressure in mmHg	Measure at baseline and at 5, 15, 30 and 60 minutes after drug administration
Pulse Rate	Pulse Rate in beat per minute	Measure at baseline and at 5, 15, 30 and 60 minutes after drug administration
Oxygen saturation	Oxygen saturation in %	Measure at baseline and at 5, 15, 30 and 60 minutes after drug administration
Level of sedation	Ramsay Sedation Scale 1-6. 1 indicates patient is anxious and agitated or restless, or both; 2 indicates patient is co-operative, oriented, and tranquil; 3 indicates patient responds to commands only; 4 indicates patient exhibits brisk response to light glabellar tap or loud auditory stimulus; 5 indicates patient exhibits a sluggish response to light glabellar tap or loud auditory stimulus; 6 indicates patient exhibits no response.	Measure at baseline and at 5, 15, 30 and 60 minutes after drug administration
Drug-related adverse events	Patients are advised to report any discomfort any time during the study period. The investigator would judge whether the complaint is drug-related and give corresponding treatment. If the patients have no active complaint, they would be asked on a checklist for possible related adverse events before discharge. The nature and severity of adverse events would be documented. To exclude any late effects, discharged patients are encouraged to return to the department if they experience any adverse events.	After drug administration until the end of the observation period (1 hour)
Use of rescue medication	Analgesics given after study drug administration in either group are considered as rescue medication. It will be given any if the patient requests or pain improvement is insufficient based on judgement of the attending physician. The name of rescue medication, dosage, time and route of administration will be documented.	After drug administration until the end of the observation period (1 hour)
Level of patient's satisfaction	Patients are instructed to rate the overall efficacy and acceptance of the drug by five-point Likert scale on a questionnaire.	After drug administration until the end of the observation period (1 hour)

Collaborators and Investigators

• Sponsor: Hospital Authority, Hong Kong
• Investigators: Principal Investigator: Ka Ying Wong, MB ChB, Hospital Authority, Hong Kong

Study record dates

Study Major Dates

• Study Start (Actual): October 28, 2020
• Primary Completion (Actual): November 21, 2020
• Study Completion (Actual): November 21, 2020

Study Registration Dates

• First Submitted: October 23, 2020
• First Submitted That Met QC Criteria: October 31, 2020
• First Posted (Actual): November 6, 2020

Study Record Updates

• Last Update Posted (Actual): December 8, 2020
• Last Update Submitted That Met QC Criteria: December 6, 2020
• Last Verified: December 1, 2020

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Pathologic Processes; Disease Attributes; Emergencies; Physiological Effects of Drugs; Molecular Mechanisms of Pharmacological Action; Central Nervous System Depressants; Peripheral Nervous System Agents; Enzyme Inhibitors; Analgesics; Sensory System Agents; Anesthetics, General; Anesthetics; Anti-Inflammatory Agents, Non-Steroidal; Analgesics, Non-Narcotic; Anti-Inflammatory Agents; Antirheumatic Agents; Cyclooxygenase Inhibitors; Anesthetics, Inhalation; Ketorolac; Methoxyflurane
• Other Study ID Numbers: HKECREC-2020-064

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No