Methoxyflurane Inhalation as an Analgesic for Minor Gynecological, Ambulatory, or Emergency Procedures
Authors: CADTH  
Published: September 2024

What Is the Issue?

Patients presenting to outpatient clinics or emergency departments often undergo procedures that cause pain.
Procedural sedation and analgesia for pain management requires a trained person to administer sedative agents and manage any drug-related complications during and after the procedures.
Inhaled methoxyflurane (Penthrox) was approved in Canada in 2022 for short-term relief of moderate to severe acute pain associated with trauma or interventional medical procedures in conscious adult patients.
Unlike conventional sedation, patients can self-administer and titrate the amount of methoxyflurane by inhaling through a 3 mL device of 99.9% methoxyflurane, which provides continuous analgesia for 25 to 30 minutes.
Decision-makers are interested in understanding the use of inhaled methoxyflurane for analgesia in minor gynecological procedures or for use in ambulatory or emergency care settings.

What Did We Do?

We identified and summarized literature on the clinical effectiveness and safety of methoxyflurane compared to placebo or other analgesics in minor medical and surgical procedures. We also searched for economic evaluations of the cost-effectiveness of methoxyflurane to manage pain during minor procedures.
We searched peer-reviewed and grey literature sources published between January 1, 2012, and July 3, 2024. One reviewer screened citations for inclusion based on predefined criteria, critically appraised the included studies, and narratively summarized the findings.

What Did We Find?

We identified 1 systematic review, 1 randomized controlled trial, 1 prospective cohort study, and 2 retrospective chart review studies that provided evidence on the efficacy and safety of methoxyflurane during various minor medical procedures, including cancer-related procedures (i.e., colonoscopy, transrectal ultrasonography-guided prostate biopsy, bone marrow biopsy, and solid organ biopsy) and other minor procedures (i.e., portacath insertion, portacath removal, and reduction of acute shoulder dislocation and acute elbow dislocation).
Collective evidence from the few studies available for each type of procedure shows that methoxyflurane is an effective analgesic that, compared with sedation, shortens the duration of both the procedure and recovery without impacting procedural success.
Methoxyflurane at the analgesic dose appears to be safe — that is, not associated with kidney or liver toxicity and resulting in fewer cardiorespiratory complications or severe adverse events — despite being more likely to cause drowsiness and dizziness compared with placebo or conventional sedation.
We did not find any studies on the clinical efficacy and safety or cost-effectiveness of methoxyflurane inhalation for the treatment of pain for minor gynecological procedures.
We did not find any studies on cost-effectiveness of methoxyflurane inhalation for the treatment of pain for minor ambulatory or emergency procedures.

What Does This Mean?

The limited studies available suggested that patient-controlled analgesia with methoxyflurane is feasible and safe for use during various ambulatory and emergency procedures.
The benefits of methoxyflurane in terms of reducing procedural and recovery time may facilitate workflow and shorten waiting lists in ambulatory and emergency care settings.
More studies are needed to provide stronger evidence on the efficacy and safety of methoxyflurane during medical and surgical procedures.