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Cost saving of switching to equivalent inhalers and its effect on health outcomes
  1. Chloe I Bloom1,
  2. Ian Douglas2,
  3. Jack Olney3,
  4. Grainne D'Ancona4,
  5. Liam Smeeth5,
  6. Jennifer K Quint6
  1. 1 National Heart and Lung Institute, Imperial College London, London, UK
  2. 2 Faculty of Epidemiology and Public Health, London School of Hygiene and Tropical Medicine, London, UK
  3. 3 Centre for Health and Economics Policy Innovation, Imperial College London Business School, London, UK
  4. 4 Pharmacy Department, Guy’s and St Thomas’ NHS Foundation Trust and King’s College London, London, UK
  5. 5 Faculty of Epidemiology and Public Health, London School of Hygiene and Tropical Medicine, London, UK
  6. 6 National Heart and Lung Institute, Imperial College London, London, UK
  1. Correspondence to Dr Chloe I Bloom, NHLI, Imperial College London, London SW3 6LR, UK; chloe.bloom06{at}


Background Switching inhalers to cheaper equivalent products is often advocated as a necessary cost saving measure, yet the impact on patient’s health and healthcare utilisation has not been measured.

Methods We identified asthma and chronic obstructive pulmonary disease (COPD) patients from UK primary care electronic healthcare records between 2000 and 2016. A self-controlled case series was used to estimate incidence rate ratios (IRR); comparing outcome rates during the risk period, 3 months after the exposure (financially motivated switch), and control periods (preswitch and postrisk period). Four outcomes were assessed: disease exacerbation, general practitioner consultation, non-specific respiratory events and adverse-medication events. Medication possession ratio (MPR) was calculated to assess adherence. 2017 National Health Service indicative prices were used to estimate cost differences per equivalent dose.

Results We identified a cohort of 569 901 asthma and 171 231 COPD regular inhaler users, 2% and 6% had been switched, respectively. Inhaler switches between a brand-to-generic inhaler, and all other switches (brand-to-brand, generic-to-generic, generic-to-brand), were associated with reduced exacerbations (brand-to-generic: IRR=0.75, 95% CI 0.64 to 0.88; all other: IRR=0.79, 95% CI 0.71 to 0.88). Gender, age, therapeutic class, inhaler device and inhaler-technique checks did not significantly modify this association (p<0.05). The rate of consultations, respiratory-events and adverse-medication events did not change significantly (consultations: IRR=1.00, 95% CI 0.99 to 1.01; respiratory-events: IRR=0.96, 95% CI 0.95 to 0.97; adverse-medication-events: IRR=1.05, 95% CI 0.96 to 1.15). Adherence significantly increased post-switch (median MPR: pre-switch=54%, post-switch=62%; p<0.001). Switching patients, in the cohort of regular inhaler users, to the cheapest equivalent inhaler, could have saved around £6 million annually.

Conclusion Switching to an equivalent inhaler in patients with asthma or COPD appeared safe and did not negatively affect patient’s health or healthcare utilisation.

  • inhaler devices
  • asthma
  • COPD epidemiology

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  • Contributors All authors provided substantial contributions to the work. CIB, ID, LS and JKQ devised the study. CIB analysed, interpreted the data and produced draft manuscripts. ID, JO and GA provided specific input for the analysis and interpretation. All authors reviewed and edited the manuscript. All were happy with the final version and approved it for submission for publication.

  • Funding This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests CIB reports grants from MRC, AsthmaUK, Chiesi and AstraZeneca outside the submitted work. ID reports grants from GSK and the British Pharmaceutical Industry outside the submitted work. JO has nothing to disclose. GA reports personal fees from AstraZeneca, BI, Chiesi, GSK,Pfizer, Napp, Novartis and Teva outside the submitted work. LS reports grants from Wellcome, MRC, NIHR, GKS, BHF and Diabetes UK outside the submitted work; reports personal fees and is a Trustee of the British Heart Foundation. JKQ reports grants from The Health Foundation, MRC, British Lung Foundation, GSK, grants and personal fees from BI, grants and personal fees from AstraZeneca, Chiesi, GSK, BI, AZ, Teva, Bayer, IQVIA and Insmed; personal fees from Chiesi, GSK, BI, AZ, Teva, Bayer and Insmed.

  • Patient consent for publication Not required.

  • Ethics approval The protocol for this research was approved by the Independent Scientific Advisory Committee (ISAC) for MHRA Database Research (protocol number 17_090RAR) and the approved protocol was made available to the journal and reviewers during peer review. Generic ethical approval for observational research using CPRD with approval from ISAC has been granted by a Health Research Authority (HRA) Research Ethics Committee (East Midlands—Derby, REC reference number 05/MRE04/87).

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement Data may be obtained from a third party and are not publicly available.

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