Evaluating the Carbon Footprint of Antibiotics Prescribed in Primary Care in Ireland
This study of Irish primary care data from 2019 to 2023 reveals that the HSE Green/Red antibiotic initiative, originally designed to combat antimicrobial resistance, concurrently drives a significant reduction in carbon emissions by aligning lower-carbon prescribing with green-listed, narrower-spectrum antibiotics.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
Every time a doctor writes a prescription, a small but measurable amount of carbon dioxide is released into the atmosphere. This happens long before the patient ever takes the pill, during the complex industrial process of creating the medicine itself. While the healthcare sector is often discussed in terms of hospital energy use or medical waste, the manufacturing of medicines accounts for a significant portion of the industry's total climate impact. Antibiotics, in particular, carry a heavy burden because they are prescribed in vast quantities and often require intricate, energy-intensive chemical pathways to synthesize. In Ireland, where primary care doctors handle the vast majority of these prescriptions, a national program was already in place to guide doctors toward safer antibiotics that reduce the risk of drug-resistant bacteria. A new study asks a simple, unexamined question: does choosing these "safer" antibiotics also happen to be the choice that is better for the climate?
Researchers from Trinity College Dublin and the Royal College of Surgeons Ireland set out to answer this by looking at the actual records of every antibiotic prescription reimbursed by the Irish health service between 2019 and 2023. They did not look at individual patients, but rather at the millions of prescription claims themselves. For each type of antibiotic, they applied a standard method that calculates the carbon footprint based on the chemical structure of the drug. This method assigns a rating from low to very high, depending on how much energy and material are needed to produce a single dose. The team then compared these carbon ratings against the existing Irish guidelines, which categorize antibiotics into a "green" list of preferred drugs and a "red" list of reserved drugs used only when necessary.
The analysis revealed a striking alignment between fighting drug resistance and fighting climate change. The study found that the "green" list, designed to protect public health, largely consists of antibiotics with a lower carbon footprint. In contrast, the "red" list is dominated by drugs that are very high in carbon emissions. In 2023, nearly three-quarters of all prescriptions for red-listed antibiotics fell into the highest carbon category, whereas less than one percent of green-listed prescriptions did. This suggests that when Irish doctors follow the existing advice to choose narrower-spectrum, green-listed antibiotics, they are incidentally making a much more environmentally friendly choice without needing new rules or extra training.
However, the story is not entirely one of success. While the overall proportion of high-carbon prescriptions dropped slightly over the five-year period, this improvement was driven almost entirely by a specific change in how doctors treated respiratory infections. In 2020, guidelines were updated to recommend a different class of antibiotics for patients allergic to penicillin, moving them away from a group of drugs called macrolides. Macrolides are chemically complex and carry a very high carbon footprint. Following the guideline change, the use of these specific drugs fell sharply, which pulled down the national average for carbon emissions. Yet, the data also shows a worrying trend: since 2021, the use of macrolides has begun to rise again. Because these drugs are all on the red list and all carry the highest carbon rating, their resurgence threatens to undo the environmental gains made in the previous years.
The researchers point out that the connection between the two goals is not perfect. There are a few exceptions where a drug is on the green list but still carries a high carbon cost, proving that the current guidelines were not designed with the climate in mind. Nevertheless, the overall pattern is clear: the structural complexity that makes some antibiotics powerful and broad-spectrum also makes them difficult and energy-intensive to manufacture. By sticking to the simpler, green-listed options, the healthcare system is already reducing its carbon output. The study concludes that making this environmental benefit explicit—by adding carbon ratings to the existing guidelines—could help doctors and pharmacists see the full picture. This would turn an accidental benefit into a deliberate strategy, allowing the medical community to tackle antimicrobial resistance and climate change with a single, unified approach.
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