Prescribing Trends for Oral Vancomycin and Fidaxomicin after Guideline and Formulary Changes in Ontario, Canada: An Interrupted Time-Series Analysis.

Background: is a pathogen causing diarrheal illness, which can be treated with vancomycin or fidaxomicin.

Objective: To evaluate changes in monthly prescription volumes for oral vancomycin and fidaxomicin in Ontario community pharmacies following implementation of the 2017 and 2021 updates to guidelines from the Infectious Diseases Society of America (IDSA) and Society for Healthcare Epidemiology of America (SHEA) and after a 2019 provincial formulary change for vancomycin.

Methods: An interrupted time-series analysis was conducted from November 2015 to October 2021 using monthly projected prescription volumes obtained from IQVIA's Compuscript database. Level and slope (trend) changes in prescribing were assessed using segmented linear regression.

Results: The volume of vancomycin prescriptions increased by 74 prescriptions per month (95% confidence interval [CI] 16 to 132) following implementation of the 2017 guideline update and by 73 prescriptions per month (95% CI 13 to 133) after the 2019 formulary change; however, no statistically significant changes were observed after implementation of the 2021 guideline update. No significant trend changes were observed for fidaxomicin.

Conclusion: Guidelines and formulary changes were correlated with increased volume of vancomycin prescriptions.