Greenhouse gas emissions higher with metered-dose vs. dry-powder, soft-mist inhalers

Key takeaways:

• Almost all of the estimated 1.15 MMT of CO₂ equivalent emissions in 2022 came from metered-dose inhalers.
• The inhaler class with the largest spending amount was dry-powder inhalers.

Metered-dose inhalers had higher estimated greenhouse gas emissions than dry-powder and soft-mist inhalers but cost less than these propellant-free inhalers, according to a research letter published in JAMA.

“Clinicians can consider prescribing inhalers with lower carbon footprints,” Jyothi Tirumalasetty, MD, clinical assistant professor at Stanford University School of Medicine, told Healio. “They also should be mindful of clinical efficacy, patient preferences and, most importantly, patient out-of-pocket costs before switching. Shared decision-making and close follow-up with each patient is ideal.”

In this study, Tirumalasetty and colleagues analyzed various U.S. brand-name and generic inhaler prescriptions given to Medicare Part D and Medicaid beneficiaries to find out how average greenhouse gas emissions and costs differ between metered-dose inhalers (n = 14), dry-powder inhalers (n = 19) and soft-mist inhalers (n = 4).

As Healio previously reported, patients with asthma who switched from a metered-dose inhaler to a dry-powder inhaler cut their inhaler carbon footprint by more than half, without loss of asthma control.

For each metered-dose inhaler, researchers multiplied weight of inhaler contents by propellant percentage and then by 100-year global warming potential of the propellant to determine emissions.

The inhaler class with the highest average estimated emissions per inhaler was metered-dose inhalers at 23.1 kg of carbon dioxide equivalent (CO₂e), whereas both dry-powder inhalers and soft-mist inhalers had smaller average estimated emissions per inhaler at 0.79 kg CO₂e and 0.78 kg CO₂e, respectively.

“10 kg CO₂e equals 41.2 km driven in an average gasoline-powered passenger vehicle,” Tirumalasetty and colleagues wrote.

When comparing an inhaled corticosteroid plus LABA metered-dose inhaler (Dulera, Organon; mometasone/formoterol) with a dry-powder inhaler of the same combination (Advair Diskus, GSK; fluticasone/salmeterol), researchers found larger emissions per inhaler with the metered-dose inhaler (48.1 kg CO₂e vs. 0.898 kg CO₂e). In contrast, the dry-powder inhaler cost more ($581.60 vs. $444.37 per Medicare claim).

The medication category within the metered-dose inhaler class with the most prescriptions was short-acting beta-agonists, which Tirumalasetty told Healio was surprising.

The class with the most CMS inhaler claims in 2022 was metered-dose inhalers (49 million; 70.2%), followed by dry-powder inhalers (17.1 million; 24.5%) and soft-mist inhalers (3.6 million; 5.2%).

Researchers multiplied mean emissions per inhaler class by number of claims per class to estimate 2022 total emissions.

Similar to above, almost all of the estimated 1.15 MMT of CO₂e emissions in 2022 came from metered-dose inhalers (1.13 MMT CO₂e emissions) vs. dry-powder (0.014 MMT CO₂e emissions) and soft-mist inhalers (0.003 MMT CO₂e emissions).

Lastly, the class with the largest spending amount was dry-powder inhalers ($10 billion; 50.8%), followed by metered-dose inhalers ($7.5 billion; 37.9%) and soft-mist inhalers ($2.2 billion; 11.3%).

“We were indeed surprised by the amount of Medicare spending on dry powder inhalers,” Tirumalasetty told Healio. “It turns out that CMS’s reported spending on dry-powder inhalers, which make up only 24.5% of claims, was approximately $2.5 billion more than spending on metered-dose inhalers, which made up 70.2% of claims in 2022.

“The punchline is that environmentally friendly inhalers are disproportionately more expensive in the U.S., making an ecological transition challenging,” Tirumalasetty added. “But more broadly, I think it speaks to the trade-offs required within health care to weigh clinical efficacy vs. environmental impact vs. cost — critical discussions that relatively few are having within U.S. medicine.”

Moving forward, Tirumalasetty said dry-powder and soft-mist inhalers should be studied further.

“We would like to see more studies that compare the clinical efficacy of dry-powder and soft-mist inhalers (both of which do not contain propellants) compared to metered-dose inhalers which do contain propellants, patient inhaler preferences and out-of-pocket inhaler costs,” Tirumalasetty told Healio.