Background
Antimicrobial consumption is the main driver of antimicrobial
resistance. Therefore, antimicrobial consumption surveillance is
important to identify potential over and inappropriate use of
antimicrobial agents.
ATC/DDD Methodology
Irish antimicrobial sales data are obtained from IQVIA (formerly IMS
Health), a pharmaceutical market research company. This dataset contains
regional, monthly wholesaler-to-community pharmacy sales data from over
95% of the wholesalers and manufacturers in Ireland.
Consumption is measured as defined daily dose (DDD), which is the
assumed average maintenance dose per day for a drug used for its main
indication in adults. The WHO Anatomical Therapeutic Chemical (ATC)
index is used to categorise antimicrobial agents. The ATC/DDD system is
recommended by WHO as the international standard for drug utilization
studies and it serves as a tool for drug utilization monitoring and
research to improve quality of drug use. More information on ATC/DDD
Methodology can be found on WHO’s website.
Consumption rates are calculated as DDD per 1000 inhabitants per day
(DID). Eurostat yearly population estimates are used for national rates.
Central Statistics Office 2022 Census results are proportionated with
Eurostat population to calculate the county rates. The underlying trend
on the quarterly graph is derived by using local regression of seasonal
results.
The WHO introduced the AWaRe classification in 2017 as part of its
Essential Medicines List to support antimicrobial stewardship
activities. This system categorizes antibiotics into three
groups—Access, Watch, and Reserve—to promote their responsible use. To
assess the relative consumption of these categories, the 2025 AWaRe
classification is applied. By 2030, the EU aims for at least 65% of
total antibiotic consumption to come from the Access group in every
Member State.
The European Surveillance of Antimicrobial Consumption Network
(ESAC-Net) is managed by the European Centre for Disease Prevention and
Control (ECDC) and the network uses the same methodology. The country
rates for the EU Member States are obtained from ECDC’s ESAC-Net
Dashboard. More information on ESAC-Net can be found on ECDC’s website.
Limitations
Although the IQVA database used in this report is very comprehensive,
there are some limitations. The data are based on pharmacy wholesale
data, rather than on individual prescriptions. Thus, it cannot be used
to determine the actual number of antimicrobial courses taken and does
not provide information on dose or duration of therapy. Factors such as
stockpiling of antimicrobials in pharmacies and drug wastage
(e.g. passing the sell-by date) may introduce biases. Likewise, recent
changes to prescribing guidelines, that recommend using higher doses may
lead to an increase in consumption (as measured by DDD/1000
inhabitants/day), while the total number of prescriptions may have
remained static or even declined.
