3 mL inhaled methoxyflurane to reduce pain during IUD insertion

A Double-blind Placebo-controlled Randomized Controlled Trial (RCT) of 3 mL Inhaled Methoxyflurane for Intrauterine Device (IUD) Insertion

This trial will see if a 3 mL dose of self‑administered inhaled methoxyflurane (Penthrox) can reduce pain and anxiety for people aged 18–55 during IUD insertion.

Quick facts

• Phase: PHASE4
• Study type: Interventional
• Enrollment: 110 (estimated)
• Ages: 18 Years to 55 Years
• Sex: Female
• Sponsor: Women's College Hospital (other)
• Locations: 1 site (Toronto, Ontario)
• Trial ID: NCT07295054 on ClinicalTrials.gov

What this trial studies

This Phase 4 interventional trial compares 3 mL inhaled methoxyflurane delivered via a Penthrox inhaler versus saline in people undergoing IUD insertion. Participants are adults with a uterus who can use an inhaler, speak English, and are willing to receive a cervical block; outcomes include patient satisfaction, procedural pain scores, anxiety levels, and adverse events. Methoxyflurane is a short‑acting, non‑narcotic, self‑administered inhaled analgesic with rapid onset that has been used in acute and procedural settings. The trial is conducted at an outpatient site to test whether this patient‑controlled approach improves the insertion experience without requiring IV access or prolonged recovery.

Who should consider this trial

Good fit: Ideal candidates are English‑speaking people aged 18–55 with a uterus who can use an inhaler, are scheduled for an IUD insertion, and are willing to receive a cervical block.

Not a fit: Patients unlikely to benefit include those who are pregnant, unable to consent, recently used opioids/benzodiazepines/cannabis or misoprostol, have a history of severe reactions to methoxyflurane or halogenated anesthetics, altered consciousness, or significant uterine anatomical distortion.

Why it matters

Potential benefit: If successful, this could provide rapid, self‑controlled pain relief during IUD insertion and improve patient comfort and satisfaction.

How similar studies have performed: Methoxyflurane has shown rapid and effective analgesia in acute trauma and other procedural settings, but its specific use for IUD insertion has limited prior data.

Eligibility criteria

Inclusion Criteria:

1. Patients with a uterus.
2. Ages 18 to 55 years.
3. Undergoing any intrauterine device (IUD) insertion.
4. English-speaking participants.
5. Ability to use an inhaler device.
6. Willing to receive a cervical block for their IUD insertion

Exclusion Criteria:

1. Inability to provide informed consent.
2. Confirmed pregnancy.
3. Use of pain medication other than NSAIDs or acetaminophen (e.g., opioids, benzodiazepines, muscle relaxants) within 24 hours prior to the intervention.
4. Use of cannabis within 24 hours prior to the intervention.
5. Administration of misoprostol within 24 hours prior to the intervention.
6. Altered level of consciousness due to any cause, including head injury, drugs, or alcohol.
7. History of severe adverse reactions to Penthrox (methoxyflurane) or other halogenated anesthetic agents, or to any ingredient in the formulation (including non-medicinal ingredients or container components).
8. Anatomical variance, such as distorted uterine cavity, bicornuate uterus, uterus didelphys, or cervical stenosis.
9. Clinically significant renal and/or liver impairment.
10. Known or genetic susceptibility to malignant hyperthermia.
11. Clinically evident hemodynamic or cardiovascular instability, or respiratory depression.
12. Not NPO according to hospital guidelines.

Where this trial is running

Toronto, Ontario

• Women's College Hospital — Toronto, Ontario, Canada (RECRUITING)

Study contacts

• Principal investigator: Lauren Scott, NP — Women's College Hospital
• Study coordinator: Didem Bozak

Conditions: IUD, Methoxyflurane, Penthrox