Introducing Penthrox for Patients Undergoing Colonoscopy

Project completed as part of the 2026 Green Gastroenterology Challenge 

Team members

Andrea Scott (Associate Chief Nursing Officer)

Mark Friend (Head of Infection Prevention and Control)

Sarah Danahar (Head of Clinical Effectiveness & Improvement)

Sarah Gibbings (Endoscopy Governance, Quality and JAG Lead/Associate Clinical Lead Portsmouth)

Inese Gredzena (Surgical First Assistant and Endoscopy Nurse, Gillingham). 

Setting / patent group: 

Practice Plus Group endoscopy services at Gillingham and Portsmouth sites covering a combined population of 3.9 million, performing 10,000 endoscopy procedures annually.  The pilot involved patients undergoing colonoscopy and flexible sigmoidoscopy who would otherwise receive Entonox or intravenous sedation/analgesia.

Issue:

Entonox is widely used for analgesia during endoscopy but contributes substantially to greenhouse gas emissions. The service identified a need to reduce the environmental impact of analgesia while maintaining patient safety, comfort and procedural effectiveness. 

Intervention: 

Penthrox (methoxyflurane) was introduced and piloted as an alternative to Entonox and intravenous sedation. The project included stakeholder engagement, baseline data collection, SOP, PGD and consent development, governance approvals, staff training, procurement processes, patient information materials and phased implementation at two pilot sites. 

Outcomes:

Clinical:

No incidents or adverse effects related to Penthrox were reported. One patient was able to complete a procedure that would otherwise have been abandoned with IV sedation. The project identified a reduction in abandoned and incomplete procedures, potentially avoiding repeat procedures and supporting more timely and effective care.

Environmental:

A full switch from Entonox to Penthrox for patients currently receiving Entonox across the two pilot sites was estimated to avoid 18,028 kgCO2e annually. A 50% switch would avoid 9,014 kgCO2e annually. The environmental benefit is primarily due to replacing nitrous oxide, a potent greenhouse gas, with a lower-carbon alternative. 

Financial:

Penthrox cost was £17.99 per patient compared with £12.17 for Entonox and £16.66 for Entonox plus IV sedation. A 100% switch from Entonox to Penthrox was estimated to increase direct consumable costs by £10,604 per year. Potential efficiency savings from reduced abandoned procedures, recovery requirements, discharge times and incident reporting could potentially offset this cost, but were not included within the scope of this project. 

Social:

Patient surveys at both sites found Penthrox easy to use, with most patients reporting effective pain relief and stating they would recommend it to others. Staff reported that Penthrox was easy to explain, assemble and administer, and could be incorporated into routine practice. The report also identified potential benefits related to patient independence, reduced need for escorts, less disruption to work and caring responsibilities, and improved workflow efficiency. 

Key learning points:

The discussion identified that successful implementation depended on strong governance arrangements, staff education, stakeholder engagement and clinical oversight. Clinical education was highlighted as one of the most important factors, helping staff understand both the clinical benefits and environmental rationale for change. Early engagement, clear communication and robust training supported rapid adoption with no significant implementation barriers identified.