Inhaled methoxyflurane (Penthrox®) as a novel pain relief for outpatient hysteroscopy and other gynaecological procedures

Objective: Penthrox® (methoxyflurane) is a convenient, portable, self-administered disposable single-use handheld inhaler licenced as an emergency, rapid-onset, short-acting, analgesic in adult trauma patients. Outpatient hysteroscopy is one of the commonest procedures in contemporary gynecology but it can be associated with significant pain leading to poor patient experience and failed procedures. We evaluated the feasibility and acceptability of Penthrox® in women undergoing outpatient hysteroscopic procedures and its potential efficacy to reduce pain and improve patient experience.

Study design: We conducted a prospective observational cohort study on women undergoing hysteroscopy or other intrauterine procedures, such as coil fitting, endometrial biopsy, polypectomy, endometrial ablation and manual vacuum aspiration in an outpatient setting. Women were offered Penthrox® inhalers for pain control, instructed how to use it and asked to record the intra-procedural pain they expected and actually experienced using a 10 cm Visual Analogue Scale. The acceptability, side effects and ease of use of the Penthrox® device were also recorded.

Results: 122/146 (83.6 %) women chose to use Penthrox®. 116 out of the 122 (95.1 %) underwent an intrauterine procedure, including 59 hysteroscopic polypectomies and 34 global endometrial ablations. The average pain expected during the procedure was 6.0 (SD = 2.8) and the pain experienced during the procedure was 5.1 (SD = 2.8). The intended procedure was completed in 117 (96 %) women. Penthrox® was considered easy to use by 118 (97 %) women and 111 (91 %) would use it again, although 22 (18 %) women would prefer general anaesthesia in the future. No adverse events occurred but 88 (72 %) women reported mild, self-limiting side effects.

Conclusion: Penthrox® appears safe, feasible and acceptable as a pain relief option during outpatient hysteroscopy and other intrauterine procedures. The effectiveness of Penthrox® should be evaluated against conventional pain control in an adequately powered multicentre randomised controlled trial.