Time series analysis of the impact of an intervention in Tayside, Scotland to reduce primary care broad-spectrum antimicrobial use.

Abstract

Concern about Clostridium difficile infection (CDI) and resistance has driven interventions internationally to reduce broad-spectrum antimicrobial use. An intervention combining guidelines, education and feedback was implemented in Tayside, Scotland in 2009 aiming to reduce primary care prescribing of co-amoxiclav, cephalosporins, fluoroquinolones and clindamycin ('4C antimicrobials'). Our aim was to assess the impact of this real-world intervention on antimicrobial prescribing rates. We used interrupted time series with segmented regression analysis to examine associations between the intervention and changes in antimicrobial prescribing (quarterly rates of patients exposed to 4C antimicrobials, non-4C antimicrobials and any antimicrobial in 2005-12). The intervention was associated with a highly significant and sustained decrease in 4C antimicrobial prescribing, by 33.5% (95% CI -26.1 to -40.9), 42.2% (95% CI -34.2 to -50.2) and 55.5% (95% CI -45.9 to -65.1) at 6, 12 and 24 months after intervention, respectively. The effect was seen across all age groups, with the largest reductions in people aged 65 years and over (58.4% reduction at 24 months, 95% CI -46.7 to -70.1) and care home residents (65.6% reduction at 24 months, 95% CI -51.8 to -79.4). There were balancing increases in doxycycline, nitrofurantoin and trimethoprim prescribing as well as a reduction in macrolide prescribing. Total antimicrobial exposure did not change. A real-world intervention to reduce primary care prescribing of antimicrobials associated with CDI led to large, sustained reductions in the targeted prescribing, largely due to substitution with guideline-recommended antimicrobials rather than by avoiding antimicrobial use altogether. Further research is needed to examine the impact on antimicrobial resistance.