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Purpose: Antibiotic therapy is essential for the treatment of cystic fibrosis (CF) lung infections. Methicillin resistant Staphylococcus aureus (MRSA) infects 20-25% of people with CF (PCF) and is associated with increased morbidity. Treatment of pulmonary exacerbations (PE) often requires hospitalization including increased respiratory treatments and IV antimicrobials. IV vancomycin (IV VANC), which is commonly used for MRSA infections, requires serum concentration monitoring to ensure efficacy and minimize toxicity. Previous monitoring guidelines used trough concentrations to predict efficacy and toxicity. Recent guidelines changed to recommend area under the curve (AUC) modeling

Methods: Children’s Mercy Kansas City (CMKC), changed IV VANC monitoring from trough to AUC measurement on 01 May 2020. A retrospective chart review collected trough monitoring data for all PCF that received IV VANC at CMKC from 01 January 2019 to 31 December 2019. Data for all PCF treated with IV VANC after the AUC monitoring change was collected through 28 February 2021. Patient demographics, details of IV VANC therapy (dose, frequency, total exposure, nephrotoxicity), and monitoring data (serum concentrations and AUC modeling) were collected. Descriptive statistics were used to assess pre- and post-implementation data.

Results: Pre-AUC, 25 patients received 42 courses of IV VANC; 14 were female (56%), and the median age was 14.02 years (4.25-20.25). Median treatment duration was 9.62 days (1.79-26.54), and median daily vancomycin exposure was 71.43 mg/kg/day (49.58-99.29). Target vancomycin trough concentration (>15 mcg/mL) was reached during 18 courses (43%). The median time to therapeutic trough was 83.58 hours (11.55-273.55) and required a median of three phlebotomies (1-9). Post-AUC there have been 15 courses of IV VANC in 8 PCF; 5 were female (63%), and the median age was 17.96 years (7.60-20.10). Median treatment duration was 9.52 days (5.68-14.63) and median daily vancomycin exposure was 75 mg/kg/day (48.63-92.80). All treatment courses reached target vancomycin AUC (400-600 mcg/mL*hr); median time of 20.13 hours (11.6-106.12) and median three phlebotomies (2-8).

Conclusions: Changing to AUC monitoring for IV VANC among PCF, was not associated with a significant change in vancomycin daily exposure or duration. There was a 60% increase in individuals achieving therapeutic targets with AUC monitoring (n=15, 100%) compared to trough monitoring (n=18,40%). AUC monitoring was associated with a decreased time to therapeutic target by 63.45 hours. A difference in nephrotoxicity was not seen. Limitations include short post-implementation period (ten months) and small sample size. Ongoing data collection is planned.

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Vancomycin Auc Monitoring In Individuals With Cystic Fibrosis