Discussion
Our study demonstrates that in a setting with a long-standing AMS program the median duration of IV antimicrobial use was short (3 days) and a majority of patients (57%) received timely IV-oral-switch. Although a substantial proportion (43%) did not receive timely IV-oral-switch, the excess IV treatment duration in these patients was typically short (median 1.75 days). Results for general medical and surgical patients were similar.
Numerous IV-oral-switch studies have been conducted in similar patient groups, however many were undertaken over two decades ago when AMS programs were in their infancy. Two recent studies examined IV-oral-switch in patient populations similar to ours. Mouwen et al. reviewed 138 (84 pre- and 54 post-intervention) surgical patients to evaluate a combination of interventions to improve IV-oral-switch. Interventions included educating physicians via a single presentation, provision of pocket-sized cards containing a flowchart of switch criteria plus additional information (e.g. indications for prolonged IV therapy), and switch advice in the electronic prescribing record [9]. The percentage of courses with timely IV-oral-switch and the median duration of IV therapy improved significantly following intervention (from 35.4% to 67.7%, and 5 to 3 days, respectively). Sze and Kong reviewed 148 medical patients (72 pre-and 76-post intervention) to evaluate printed IV-oral-switch guidelines and recommendations attached to the medical notes of patients on the day they became eligible for switch [10]. The proportion of IV-to-oral switches that occurred in a timely manner significantly increased from 24.1% to 88.3% post-intervention, and delays to switching (mean days between switch and when switch criteria were met) fell from 1.8 days to 0.2 days. The median duration of IV therapy was also significantly shorter, falling from 4.1 to 2.8 days. In our study, the median duration of IV therapy was shorter than the baseline (pre-intervention) findings of these two recent studies (3.0 days versus 4.1-5.0 days), and comparable to their post-intervention findings (3.0 days versus 2.8-3.0 days). The percentage of courses switched in a timely manner approximated the post-intervention results of Mouwen et al. [9] but was lower than that of Sze and Kong [10]. A limitation of Sze and Kong’s study, however, is that the post-intervention data collection occurred immediately after implementation of IV-oral-switch interventions, so the longer-term effects are unknown.
To the best of our knowledge ours is the first study to examine usual practice within a long-standing environment of tightly regulated AMS and IV-oral-switch guidelines. Our findings are important given post-intervention audits in previous studies were undertaken soon after IV-oral-switch interventions were implemented and thus may not reflect longer-term outcomes. This is illustrated by findings from van Niekerket al. who reported that a significant improvement in timely IV-to-oral switch after implementation of an IV-oral-switch guideline (from 16%, 19/119 to 43%, 47/107) was not sustained three months later, when IV-oral-switch rates had returned close to the pre-intervention level (20.8%, 25/120) [11].
A limitation of our study was the lack of a comparison group not exposed to our AMS program. We are unable to ascertain which element(s) of our multi-faceted AMS approach contributed to the findings of generally short IV treatment duration and timely IV-oral-switch. Studies have shown improved IV-oral-switch practice with a combination of interventions including prescriber education, printed guidelines inserted in patients’ case notes, reminder stickers on medication charts, prospective audit and feedback and electronic alerts [3], [5], [9, 10, 11, 12, 13]. Unfortunately, few IV-oral-switch studies have described what AMS programs were already in place prior to the IV-oral-switch intervention, making comparisons difficult. Given that the two most commonly prescribed IV antimicrobials in our study (ceftriaxone and amoxicillin-clavulanate) were agents requiring prior approval before prescribing, it’s likely our preauthorization system (with time-limited approvals) helped ensure IV-oral-switch was considered by day 2–3 of therapy. Preauthorization has been shown to optimise empiric choices, reduce antibiotic use and costs, increase rates of susceptible pathogens and decrease rates ofClostridioides difficile infection [14], [15]. However, to the best of our knowledge no studies have specifically examined preauthorization as a strategy to improve other AMS targets such as timing of IV-oral-switch.
An interesting finding of our study concerns the total duration (IV plus oral) of antimicrobial therapy. There is growing evidence that shorter therapy durations are as effective as longer durations for common infections [16]. We found that 45% of patients received an excessive total duration of therapy, and this may underestimate the magnitude of this issue. For example, at the time of our study national antimicrobial prescribing guidelines recommend seven days of treatment for community-acquired pneumonia (CAP) [8]. However, these guidelines recently changed to incorporate a shorter duration of five days for mild to moderately severe CAP based on recent evidence [17, 18]. There were fifteen (14.0%) patients with CAP in our cohort that received antibiotic treatment for a median of seven days. Longer durations of therapy are associated with increased risk of antimicrobial resistance, secondary infections and greater costs [19, 20, 21]. Therefore, future AMS activities should incorporate the most recent evidence for treatment duration to further optimise therapy and reduce associated hazards.
In summary, the practice of IV-oral-switch at our hospital was generally concordant with guidelines, suggesting that a tightly regulated AMS program with preauthorisation for target IV antimicrobials may lead to sustained good IV-oral-switch practice. Total duration of therapy was identified as an AMS target to improve antimicrobial prescribing and patient safety.
  1. Acknowledgement: We would like to acknowledge Associate Professor Jason Trubiano for his contribution to this manuscript.
  2. Conflict of interest: None to declare
  3. Funding: This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
  4. Data availability statement: The data that support the findings of this study are available from the corresponding author upon reasonable request.
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Table caption: Table 1: Characteristics of patients and antimicrobial use