Cost effectiveness of amoxicillin for lower respiratory tract infections in primary care: an economic evaluation accounting for the cost of antimicrobial resistance

Raymond Oppong, Richard D Smith, Paul Little, Theo Verheij, Christopher C Butler, Herman Goossens, Samuel Coenen, Michael Moore, Joanna Coast

Lower respiratory tract infections (LRTIs) are a major disease burden and are often treated with antibiotics. Typically, studies evaluating the use of antibiotics focus on immediate costs of care, and do not account for the wider implications of antimicrobial resistance. This study sought to establish whether antibiotics (principally amoxicillin) are cost effective in patients with LRTIs, and to explore the implications of taking into account costs associated with resistance. Multinational randomised double-blinded trial in 2060 patients with acute cough/LRTIs recruited in 12 European countries. A cost-utility analysis from a health system perspective with a time horizon of 28 days was conducted. The primary outcome measure was the quality-adjusted life year (QALY). Hierarchical modelling was used to estimate incremental cost-effectiveness ratios (ICERs). Amoxicillin was associated with an ICER of €8216 (£6540) per QALY gained when the cost of resistance was excluded. If the cost of resistance is greater than €11 (£9) per patient, then amoxicillin treatment is no longer cost effective. Including possible estimates of the cost of resistance resulted in ICERs ranging from €14 730 (£11 949) per QALY gained - when only multidrug resistance costs and health care costs are included - to €727 135 (£589 856) per QALY gained when broader societal costs are also included. Economic evaluation of antibiotic prescribing strategies that do not include the cost of resistance may provide misleading results that could be of questionable use to policymakers. However, further work is required to estimate robust costs of resistance.