Original research
Environmental impact Factors such as the environmental harm should be considered by clinicians when deciding on which agent to use. 24 This detailed LCIA has shown that Penthrox is better, from a climate change impact perspective by a factor of 117.7, than using 30 min of Entonox. 21 23 Another advantage of inhaled methoxyflurane is that it is not delivered by a potentially wasteful pipe system. Multiple NHS hospitals report millions of litres of annual N 2 O leakage, totalling up to 95% of the total annual collective volume. 25 Opioid analgesics might be considered in some scenarios where methoxyflurane could also be used, such as in trauma. For a 70 kg adult requiring 7 mg intravenous morphine, the climate change impact would be 0.01 kg CO 2 e. Furthermore, Pearson found two doses of intramuscular morphine to have a climate change effect of 0.08 kg CO 2 e, a similar impact to Penthrox. No data for comparing equivalent doses of intramuscular morphine and methoxyflurane on analgesic effect were found online. From these studies, we can appreciate that morphine has a lower carbon footprint. This could be a factor to consider when deciding which analgesic to use, while also acknowledging that time to peak effect of intravenous morphine is longer (15 min compared with 9 min for methoxyflurane) and has its own side- effect profile. 9 Financial impact The procurement and additional equipment costs of use of 3 mL unit of Penthrox, Entonox and intravenous morphine were £18.89, £6.60 and £7.70, respectively. 26 The disparity in price between these products means that fiscally focussed health services may find it difficult to move from the cheap cost of N 2 O and morphine products to the more expensive single unit Penthrox dispenser. However, large healthcare trusts have signif- icant market sway over procurement contracts, and there is a potential deal to be done on bulk purchasing pharmaceuticals with a smaller environmental impact. Social (clinical) impact Current evidence suggests that both N 2 O and methoxyflurane are good options for acute pain in the ED when compared with placebo pain management, with neither showing superiority. 27 Both drugs are in regular use worldwide in prehospital care, community health, dentistry and in hospitals. However, N 2 O is still used far more than methoxyflurane, despite its large carbon footprint. 10 Both are self-administered, self-titrated and non-invasive inhalational agents which are well tolerated with similar onset times for analgesia. Methoxyflurane is easily administered via a handheld device whereas N 2 O can be more difficult with either a heavy cylinder or a piped supply being required as well as a demand valve. Morphine has the added benefit of being available in multiple different formats so that it can be administered in the most appropriate form for the clinical picture. Although the comparative environmental footprint of Penthrox is low, manufacturers should look at ways of deliv- ering it more sustainably. Penthrox has many different types of plastic, as is evident from figure 2. If plastic recycling was widely available in healthcare settings, it would have to be clear which uncontaminated parts could be recycled safely. Further research and discussion with the manufacturer, local recycling contractors and clinicians would help to clarify this.
Figure 4 Normalised impact of Penthrox across impact categories.
Comparative analysis of Penthrox Using the climate change impact result from table 1, a compar- ison with an equivalent dose of Entonox and morphine sulfate could be made from other sources (figure 5) 21 22 ; 117.7 times more CO 2 e is produced when Entonox is used (raw value 98.89 kg CO 2 e) compared with Penthrox (0.84 kg CO 2 e). Intrave- nous morphine (7 mg) produces 0.01 kg CO 2 e. For perspective, a plane journey from Newcastle Airport to London Heathrow Airport produces 120.2 kg CO 2 e, a train journey from Newcastle Central Station to London King's Cross produces 23.1 kg CO 2 e and a car journey from Newcastle Central Station to London King's Cross (distance 441.6 km), with a single passenger, in a gasoline conventional, produces 80.3 kg CO 2 e. These values are represented in figure 5. DISCUSSION This detailed LCIA has calculated the environmental impact of Penthrox over 16 impact categories. This allows all those involved with its manufacture and use to fully understand its environmental impact and allows for comparison with other analgesics. When considering any healthcare intervention, we should consider the environmental (planet), financial (profit) and social/clinical/therapeutical (people) element, the so-called triple bottom line of sustainable healthcare. Each of these will be discussed in turn.
Figure 5 Comparison of climate change impact of Penthrox and other analgesics. Other analgesics include Entonox continuous use for 30 min at rate of 14 L/min and 7 mg of 100 mg in 100 mL morphine sulfate. In addition to this, we have included comparative data for a flight, car journey and train journey between Newcastle and London.
Martindale AEV, et al . Emerg Med J 2024; 41 :69–75. doi:10.1136/emermed-2022-213042
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