(283) The Impact of Guideline and Formulary Changes on Prescribing of Oral Vancomycin and Fidaxomicin for Treatment of Clostridioides Difficile Infections in Ontario Canada
PhD Student, Early Career Scholar-Pharmacist University of Waterloo/ Women's College Hospital/ University of Toronto Toronto, Canada
Background: Clostridioides difficile (C. difficile) is a gram-positive spore forming bacterium known to cause severe diarrheal illnesses. Treatment for non-fulminant C. difficile has evolved to favour vancomycin or fidaxomicin given orally over metronidazole due to improved efficacy and tolerability.
Objectives: To assess changes in prescribing of vancomycin and fidaxomicin oral formulations in Ontario, Canada, following new practice guidelines and altered public drug coverage (removal of written approval requirements).
Methods: Design and Setting: An interrupted time series analysis using monthly (2015-2021) projected total retail dispensations from IQVIA’s Compuscript database. Interventions: (1) Infectious Diseases Society of America (IDSA) and Society for Healthcare Epidemiology (SHEA) guideline released Feb 2018 (vancomycin or fidaxomicin preferred over metronidazole); (2) Change in provincial coverage in Sep 2019 for vancomycin; (3) IDSA/SHEA guideline update in Jun 2021 suggesting fidaxomicin preferentially. Main outcome measure: Total projected monthly prescription volume for vancomycin and fidaxomicin. Statistical analysis: Changes in the level and trend of monthly total projected prescription volumes of vancomycin and fidaxomicin following the 3 interventions were estimated using a segmented linear regression model.
Results: In Nov 2015 there was a total projected monthly volume of 430 oral vancomycin and 10 fidaxomicin prescriptions in Ontario. After intervention 1, the projected volume for vancomycin increased by 56 (95% CI 3, 110) then by an average of 10 (95% CI 6, 14) prescriptions monthly. Another level increase was observed after drug coverage change (intervention 2) of 86 (95% CI 29, 143) vancomycin prescriptions per month and a steady but nonsignificant increase was observed thereafter. After intervention 3, there was neither a level change nor trend shift for the projected volume of vancomycin prescriptions, however few data points are available for this period. For fidaxomicin, none of the level or slope changes were statistically significant for intervention 1 or 3; however, following intervention 2, there was a decrease of 9 prescriptions (95% CI -16, -2) per month with no significant changes in trend. The plotted data suggests increase over time from first to last year, however these analyses may be underpowered.
Conclusions: The introduction of guidelines suggesting preferred use of fidaxomicin or vancomycin for C.difficile treatment and a drug coverage policy change had a significant impact on vancomycin prescribing in Ontario. The changes overtime speak to the importance of guidelines and policy responses to uptake of most current evidence into practice.
