Methoxyflurane for IUD Insertion and Endometrial Biopsy

A Double-blind Placebo-controlled Randomized Controlled Trial (RCT) of 3ml Methoxyflurane for Intrauterine Device (IUD) Insertion and Endometrial Biopsy

The aim of this study is to determine if 3ml of inhaled Methoxyflurane, in the form of a Penthrox inhaler, reduces pain during IUD insertion and/or endometrial biopsy. The proposed study is a double-blind, placebo-controlled RCT.

Each participant will be randomly assigned to one of two arms:

1. Intervention (3ml of Methoxyflurane via a Penthrox inhaler)
2. Placebo (3ml of normal saline via an identical placebo Penthrox inhaler)

The primary outcome is global pain score, which will be patient-reported by the 100 mm Visual Analogue Scale (VAS) 5-minutes following the procedure (endometrial biopsy or IUD insertion).

Inclusion Criteria

• Any participant ≥18 years and ≤ 65 years presenting for an IUD insertion or endometrial biopsy
• For IUD insertion, only nulliparous patients
• English speaking participants only
• Availability of a ride home from the appointment

Exclusion Criteria

• Use of pain medication that is not an NSAID or acetaminophen (e.g. opioids, benzodiazepines) within past 24 hours
• Misoprostol administration within 24 hours
• Breastfeeding
• Any diagnosed chronic pain syndromes (e.g. fibromyalgia, vaginismus)
• Allergy to methoxyflurane
• Renal or liver disease
• Known or genetically susceptible to malignant hyperthermia or a history of severe adverse reactions in either patient or relatives
• Baseline vital signs of systolic blood pressure <100, diastolic blood pressure <60 and/or pulse <60.
• Previous unsuccessful office attempt of IUD insertion or endometrial biopsy by the same practitioner (note of clarification: previous unsuccessful IUD insertion or biopsy attempt by a different practitioner will still be eligible)
• Clinically evident respiratory impairment