Vancomycin is a glycopeptide antibiotic frequently used for the treatment of acute bacterial skin and skin structure infections (ABSSSI). In 2009, the American Society of Health System Pharmacists and Infectious Disease Society of America (IDSA) provided guidelines for vancomycin dosing and monitoring. However, these guidelines did not provide specific trough goals for uncomplicated ABSSSI but stated that, for uncomplicated bacterial infections, providers should aim for a trough goal of at least 10 mg/L (expert opinion, level of evidence and grade: IIIB) to decrease the risk of vancomycin-intermediate Staphylococcus aureus.

The 2009 guidelines stated that monitoring of vancomycin troughs is not necessary for treatment durations of less than 3–5 days (level of evidence and grade: IIb).1 In 2020, the American Society of Health System Pharmacists/IDSA updated their guidelines recommending a ratio of 24-hour area ORIGINAL RESEARCH Necessity of vancomycin trough concentrations for ABSSSIs Merker A, Anne K, Rayyan J, Murray M. Drugs Context.2023;12:2023-2-1. 2 of 7 ISSN: 1740-4398 under the curve to minimum inhibitory concentration of between 400 and 600 mg×h/L for serious methicillinresistant S. aureus (MRSA) infections.2 Similar to the 2009 guidelines, uncomplicated ABSSSI management was not specifically discussed.

Several clinical studies reported no difference in clinical outcome for vancomycin concentrations below and above 10 mg/L, as the mean vancomycin treatment duration was longer (7.0–7.8 days) than the 3–5 day recommendation for monitoring trough concentrations.3–6 Furthermore, vancomycin-induced acute kidney injury (AKI) has been a potential concern. However, incidence has appeared to be low in patients with trough goals <20 mg/L, those with no baseline renal impairment, those receiving short courses of vancomycin therapy (<7 days), or in those not receiving concomitant nephrotoxic agents.7–12 Finally, the guidelines recommend trough goals >10 mg/L to prevent potential vancomycin resistance; however, the literature supporting this recommendation is based on administering vancomycin for severe infections and managing MRSA and for extended therapy durations (over 14 days).

As healthcare institutions continually look for measures to reduce costs, laboratory stewardship should be a consideration. The Society of Hospital Medicine includes the avoidance of repetitive complete blood counts and chemistry testing in stable patients as part of its ‘Choose Wisely’ campaign.

Overutilization of inpatient laboratory tests is well documented, and the overutilization of tests can lead to costly downstream spending.With minimal clinical data available to support vancomycin trough monitoring for short durations of therapy, there may be decreased vancomycin trough concentration utility in certain clinical conditions.

The objective of this study was to determine if vancomycin treatment duration differs for patients with ABSSSI with a sub-therapeutic vancomycin trough (ST; <10 mg/L) compared with therapeutic trough (TT; ≥10 mg/L). Methods This was a retrospective cohort study of adult patients admitted to a general medicine unit at Mount Sinai Hospital, an urban, 319-bed, teaching hospital (Chicago, IL) and who received vancomycin for the management of an uncomplicated ABSSSI from January 1, 2016, through December 31, 2018.

During this period, recommended monitoring for vancomycin for ABSSSI at our institution included dosing towards a low trough goal (10–15 mg/L). A vancomycin trough was defined as a level having been obtained approximately 60 minutes before the fourth dose to be administered.

Dosing recommendations and adjustments were led by clinical pharmacists at the study hospital. Eligible patients had to have an admission creatinine clearance rate (CrCl, Cockcroft–Gault) ≥50 mL/minute, received scheduled vancomycin, and had a recorded trough (defined as a concentration obtained within 90 minutes before the third or fourth dose). Exclusion criteria were vancomycin administration duration of more than 5 days, documented trough goal of 15–20 mg/L, or AKI (serum creatinine >120% baseline) that did not resolve within 24 hours of initial vancomycin administration.

A complete description of inclusion and exclusion criteria is presented in Table 1. The institutional review board at Mount Sinai Hospital (Study 19-02) approved this study. At this institution, the vancomycin policy recommends trough levels before the fourth or fifth dose regardless of underlying indication.

Inclusion and exclusion criteria. Inclusion criteria Exclusion criteria • Adult general medicine patients • Initial creatinine clearance (Cockroft–Gault) ≥50 mL/minute • Received scheduled vancomycin • At least one obtained vancomycin trough (obtained within 90 minutes before the third or fourth dose) • Acute kidney injury (serum creatinine >1.2× baseline) without 24-hour resolution • Received vancomycin for >5 days • Confirmed methicillin-resistant Staphylococcus aureus infection • Patient required intensive care unit admission or transfer • Patient required emergent surgery for source control or limb amputation • Vancomycin trough goal 15–20 mg/L • Peripheral arterial or vascular disease • Infections due surgical or post-traumatic site, burns, diabetic foot ulcers, wounds, or chronic skin ulcers • Pregnancy • Vancomycin required for other infectious causes • Vancomycin discontinued for growth of only gram-negative organisms • Vancomycin discontinued for infusion reactions ORIGINAL RESEARCH Necessity of vancomycin trough concentrations for ABSSSIs.

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