3 mL Inhaled Methoxyflurane for Intrauterine Device (IUD) Insertion

Women's College Hospital

Status and phase: Not yet enrolling; Phase 4

Conditions: IUD

Treatments: Drug: Penthrox; Drug: Saline

Study type: Interventional

Funder types: Other

Identifiers

NCT07295054

2025-0056-B

Details and patient eligibility

About

Intrauterine device (IUD) insertion is a common contraceptive procedure often associated with moderate to severe pain, particularly among nulliparous individuals. Current pain management strategies, such as over-the-counter analgesics, are frequently inadequate. Methoxyflurane, a short-acting, self-administered inhaled analgesic, has been shown to provide rapid and effective pain relief in acute and procedural settings. This study aims to evaluate whether 3 mL of inhaled Methoxyflurane (via Penthrox inhaler) improves patient satisfaction by reducing pain and anxiety during IUD insertion.

Full description

Methoxyflurane is a short-acting, self-administered inhaled analgesic that has demonstrated rapid and effective pain relief in acute trauma, emergency, and procedural settings. It is non-narcotic, allows patients to control dosing, and does not require intravenous access or prolonged recovery, making it suitable for short outpatient procedures. Existing studies indicate that Methoxyflurane provides faster onset of pain relief compared to standard analgesics, is generally well-tolerated, and has only transient, non-serious adverse effects such as dizziness or headache.

This study aims to evaluate the efficacy of 3 mL of inhaled Methoxyflurane, delivered via Penthrox inhaler, in reducing pain and anxiety during IUD insertion. The primary objective is to assess patient satisfaction with pain management. Secondary outcomes include procedural pain scores, anxiety levels, and the incidence of adverse events. This trial seeks to provide evidence for an effective, safe, and patient-centered approach to pain management during IUD insertion, potentially improving patient experience and access to long-acting contraceptive options.

Enrollment: 110 estimated patients

Sex: Female

Ages: 18 to 55 years old

Volunteers: No Healthy Volunteers

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.

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.

Trial design

Primary purpose: Treatment

Allocation: Randomized

Interventional model: Parallel Assignment

Masking: Triple Blind

---

110 participants in 2 patient groups, including a placebo group

Intervention Group

Experimental group

Description:

Participants will receive a Penthrox inhaler containing 3 mL of methoxyflurane. Before speculum insertion, they will take intermittent inhalations every 30-60 seconds (6-10 breaths), following monograph instructions. They may continue self-administering the inhaler as needed during the procedure.

Treatment:

Drug: Penthrox

Placebo Group

Placebo Comparator group

Description:

Participants will receive an identical-looking inhaler containing 3 mL of normal saline. To maintain blinding, a drop of methoxyflurane will be placed on the outside of the device, which has no analgesic effect. Before speculum insertion, participants will take intermittent inhalations every 30-60 seconds (6-10 breaths), following monograph-style instructions, and may continue self-administering as needed during the procedure.

Treatment:

Drug: Saline