ABSTRACT Drug shortages pose a clear detriment to antimicrobial stewardship (AS) efforts. Our objective was to evaluate the effect of a piperacillin-tazobactam shortage on meropenem use, related costs, and associated changes in AS activity. A quasi-experimental quality improvement review compared adult patients receiving meropenem ≥72 h three months pre-shortage and three months during the shortage. 320 patients were included (pre-shortage: 103; shortage: 217). Baseline characteristics were similar, but the length of stay was slightly longer in pre-shortage [19 (11-32) days] versus shortage [16 (11-32) days] (p = 0.094). In pre-shortage and shortage, median days of therapy and estimated meropenem cost were 7 (5-11) and 7 (5-10) and $309.93 ($173.60-$507.03) and $255.30 ($204.24-$424.31), respectively (p = 0.411 and p = 0.050). Frequency of ID consultation was similar (16.8% in pre- and 25.3% in shortage, p = 0.091). AS interventions increased during the shortage period (99 in pre-shortage and 205 in shortage). De-escalation occurred in 19.4% versus 32.7% of the patients in pre-shortage and shortage (p = 0.014). The piperacillin-tazobactam shortage was associated with a 111% increase in meropenem prescriptions despite active AS, but was not associated with changes in mortality, length of therapy, or meropenem costs. AS should be aware that shortages may require proactive countermeasures to avoid inappropriate antimicrobial use during shortage periods.

Several studies have demonstrated that piperacillin/tazobactam produces a false-positive result for the galactomannan antigen test. However, the most recent literature has demonstrated that this interaction is no longer a concern. There is little information regarding the drug–laboratory interaction with the generics of piperacillin/tazobactam or other broad-spectrum beta-lactams, such as ceftaroline, doripenem, imipenem/cilastatin, and meropenem. The purpose of this study was to determine if a drug–laboratory interaction exists with these antibiotics. Tests showed that one lot of imipenem/cilastatin by Hospira Healthcare India Private Limited produced a false-positive result for the galactomannan antigen test. All other medications tested, including piperacillin/tazobactam from seven manufacturers and imipenem/cilastatin by Hospira Inc., did not produce positive results. Since the reason for this drug–laboratory interaction with imipenem/cilastatin is unknown, more studies are needed to further investigate this interaction. Providers also should be educated of these findings: no drug–laboratory interaction with piperacillin/tazobactam and a possible drug–laboratory interaction with imipenem/cilastatin (Hospira Healthcare India Private Limited).