Antibiotic utilisation and the impact of antimicrobial resistance action plan on prescribing among older adults in New Zealand between 2005 and 2019

Purpose The objectives of this study were to examine the overall utilisation of systematic antibiotics and the impact of the launch of the antimicrobial resistance action plan in older adults (65 years or more) living in New Zealand between 2005 and 2019, using data from a national database (Pharmaceutical collections), stratified by antibiotic class, patient age, and sex. Methods Population-level systemic antibiotic dispensing data for older adults in New Zealand was analysed using repeated cross-sectional analysis between 01/01/2005 and 31/12/2019. Data were extracted on the prescribed systemic antibiotics using a unique identifier for each case. Antibiotic utilisation was measured in DDD/TOPD values. In addition, an interrupted time series (ITS) analysis using the autoregressive integrated moving average (ARIMA) models was performed to determine the impact of the antimicrobial resistance action plan. Results Most of the antibiotic classes included in this study showed a significant overall decrease in utilisation ranging from 38.64% for sulphonamides to 80.64% for fluoroquinolones compared to 2005. Systemic antibiotic utilisation decreased by 49.6% from the predicted usage between January 2018 and December 2019 following the launch of the antimicrobial resistance action plan. ARIMA model supported the reduction in utilisation with a step change of -0.2206 and slope change of -0.0029. Conclusions The ITS analysis has demonstrated that the intervention may have hugely impacted the antibiotic utilisation rate among older adults. Further studies are required to determine whether the reduced consumption rates of antibiotics are associated with reduced rates of antibiotic-associated adverse drug events such as acute kidney injury and haematological abnormalities. ### Competing Interest Statement The authors have declared no competing interest. ### Clinical Trial NA ### Funding Statement The author(s) received no specific funding for this work. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The Departmental Research and Ethics Officer at the University of Bath assessed the ethical implications of research activity (EIRA) and approved this study on behalf of the University of Bath's Research, Integrity, and Ethics committee. Approval number EIRA 1-4048 I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes Data availability: The data is owned by the Analytical Services, Ministry of Health, New Zealand, so supporting data is not available.