Criteria Restricting Inappropriate Meropenem Empiricism (CRIME): a quasi-experimental carbapenem restriction pilot at a large academic medical centre

•Meropenem utilisation was evaluated in a 617-bed academic medical centre.•Restriction criteria significantly decreased inappropriate meropenem utilisation.•Length of stay, duration of meropenem use and cost were significantly reduced. The broad-spectrum activity of carbapenems makes them appealing for empirical use; however, they are associated with development of Clostridioides difficile infection (CDI) and multidrug resistance. Selective carbapenem use is vital in maintaining their effectiveness. We examined the impact of meropenem restriction criteria on utilisation and patient outcomes. This quasi-experimental study was conducted at a single academic medical centre after medication use evaluation found frequent inappropriate meropenem utilisation. Antimicrobial stewardship-led restriction criteria were developed and implemented in February 2022. Investigators aimed to determine how restriction criteria affected meropenem utilisation across 8 weeks in the pre- (February–April 2020) versus post-implementation period (February–April 2022). The primary outcome was inappropriateness of meropenem utilisation. Secondary outcomes included days of therapy per 1000 patient-days (DOT/1000 PD), hospital length of stay (LOS), CDI Standardized Infection Ratio (SIR), and acquisition cost. Across the 8-week timeframes, reductions in inappropriate meropenem use (64.5% vs. 12.8%; P < 0.001), duration of therapy [5.8 (3.2–7.3) vs. 2.4 (1.0–5.5) days; P < 0.001] and utilisation (30.5 vs. 8.3 DOT/1000 PD; P < 0.001) pre- versus post-implementation were observed. Total meropenem orders decreased by 65% (P < 0.001). Median hospital LOS also decreased between periods [11.9 (7.8–20.4) vs. 9.2 (5.4–15.2) days], although not statistically significant (P = 0.051). There was no difference in CDI SIR (0.1 vs. 0.1; P = 0.99). Projected annual cost savings were ∼US$57 300. Implementation of antimicrobial stewardship-initiated restriction criteria can reduce inappropriate meropenem utilisation, overall number of orders, and total duration of therapy.