The effectiveness of Check of Medication Appropriateness for antimicrobial stewardship: an interrupted time series analysis

Inappropriate prescribing of antimicrobials in hospitals contributes to the emergence of resistance and adverse drug events. To support antimicrobial stewardship (AMS), clinical decision rules focusing on antimicrobial therapy were implemented in the 'Check of Medication Appropriateness' (CMA). The CMA is a hospital-wide pharmacist-led medication review service consisting of a clinical rule-based screening for potentially inappropriate prescriptions (PIPs). We aimed to investigate the impact of the CMA on antimicrobial prescribing. An interrupted time series study was performed at the University Hospitals Leuven. The pre-implementation cohort was exposed to standard-of-care AMS. Afterwards, an AMS-focused CMA comprising 41 specific clinical rules, targeting six AMS objectives, was implemented in the post-implementation period. A regression model was used to assess the impact of the intervention on the number of AMS-related residual PIPs between both periods. The total number of recommendations and acceptance rate was recorded for the 2 year post-implementation period. Pre-implementation, a median proportion of 75% (range: 33%-100%) residual PIPs per day was observed. After the CMA intervention, the proportion was reduced to 8% (range: 0%-33%) per day. Use of clinical rules resulted in an immediate relative reduction of 86.70% (P