Penthrox for IUD Insertion
Penthrox (methoxyflurane) is not mentioned in the most recent 2025 American College of Obstetricians and Gynecologists guidelines for IUD insertion pain management, and therefore cannot be recommended as a standard analgesic option for this procedure based on current best practice guidelines 1.
Why Penthrox Is Not Recommended for IUD Insertion
The comprehensive 2025 AJOG guidelines systematically reviewed all available pain management strategies for IUD insertion and do not include inhaled methoxyflurane among recommended options. The guideline specifically recommends:
First-Line Analgesic Options (Based on 2025 Guidelines):
- Oral naproxen 550 mg taken 1-2 hours before the procedure 1
- Oral ketorolac 20 mg taken 40-60 minutes before, or intramuscular ketorolac 30 mg given 30 minutes prior 1
- Topical anesthetics: EMLA cream (5 mL of 2.5% lidocaine/2.5% prilocaine) applied 5-7 minutes before, or 10% lidocaine spray applied 3 minutes before 1
- Intracervical block (ICB): 2-4 mL of 1-2% lidocaine injected at cervical sites 1
- Paracervical block (PCB): Buffered 1% lidocaine at cervicovaginal junction 1
For Anxiolysis (Not Direct Pain Relief):
- Oral midazolam 10 mg taken 30-60 minutes beforehand (preferred due to fast onset and short half-life) 1
- Alternatives: lorazepam 1-2 mg sublingual or diazepam 5-10 mg oral 1
Evidence on Penthrox in Gynecological Procedures
While one 2024 observational study evaluated Penthrox in outpatient hysteroscopy and found it "feasible and acceptable," this was not a randomized controlled trial and the authors themselves concluded that "effectiveness should be evaluated against conventional pain control in an adequately powered multicentre randomised controlled trial" 2. This study showed:
- Pain decreased from median NRS 8 to 5 within 10 minutes
- 72% experienced mild, self-limiting side effects
- Only 91% would use it again, with 18% preferring general anesthesia in future
Critical limitation: This study did not compare Penthrox to any of the guideline-recommended options for IUD insertion, and hysteroscopy is a different, typically longer procedure than IUD insertion.
Important Caveats About Penthrox
The FDA labeling for Penthrox (pentoxifylline) provided in the evidence appears to be for a different drug entirely - an oral medication for peripheral arterial disease, not the inhaled methoxyflurane analgesic 3. This highlights confusion in nomenclature and underscores the lack of established FDA approval or guidelines for inhaled methoxyflurane in IUD insertion.
What Actually Works for IUD Insertion Pain
The evidence-based approach prioritizes:
Pre-procedure (1-2 hours before): Naproxen 550 mg or ketorolac 20 mg orally 1
Immediately before procedure:
For high-risk patients (nulliparous, high anxiety, previous failed insertion):
Post-procedure: Scheduled NSAIDs (naproxen 440-550 mg every 12 hours or ibuprofen 600-800 mg every 6-8 hours) for first 24-72 hours 1
Bottom Line
Use the guideline-recommended options above rather than Penthrox for IUD insertion. The 2025 expert consensus based on systematic evidence review does not support methoxyflurane use for this indication. The available evidence for Penthrox in gynecological procedures is limited to one observational study in a different procedure type, lacks comparison to standard treatments, and the authors themselves call for proper randomized trials before drawing conclusions about effectiveness 2.
If a patient specifically requests non-invasive, non-injection options, topical lidocaine preparations (EMLA cream or 10% lidocaine spray) are the evidence-based choices 1, not inhaled methoxyflurane.