Effect of oral vancomycin dose on outcomes in patients with Clostridioides difficile infection

•Vancomycin doses for Clostridioides difficile infection (CDI) vary in clinical practice despite guideline recommendations.•Few data exist regarding the optimal dosing of vancomycin in the treatment of CDI.•Clinical outcomes were compared between standard and high-dose vancomycin regimens.•Rates of recurrence, clinical failure, re-admission and mortality were similar between groups. Clostridioides difficile infection (CDI) is a significant cause of morbidity and mortality. Oral vancomycin is a cornerstone of CDI treatment, but dosing strategies in clinical practice may differ from guideline recommendations. This study aimed to determine differences in outcomes between patients treated with standard (125 mg QID) and high-dose (≥250 mg QID) oral vancomycin. This dual-centre study evaluated adult patients admitted between January 2013 and July 2017. Patients were included in the study if they had a positive C. difficile toxin PCR, symptomatic infection and received ≥48 h of oral vancomycin. Disease severity was characterised using a variety of classifiers, including guideline definitions. The primary outcome was 90-day CDI recurrence; secondary outcomes included clinical failure, in-hospital mortality and 90-day re-admission. Inverse probability of treatment weighting (IPTW) was conducted to balance differences between groups. A total of 535 patients were included; 261 received standard and 274 received high-dose vancomycin. Baseline demographics were similar between groups, except that patients receiving high-dose vancomycin were more likely to have more severe disease and to be admitted to the ICU. Few patients had fulminant disease (14.4%). No significant differences in recurrence (OR, 1.52, 95% CI 0.82–2.84), clinical failure (OR, 0.64, 95% CI 0.328–1.26), mortality (OR, 1.44, 95% CI 0.78–2.66) or re-admission (OR, 1.03, 95% CI 0.70–1.51) were identified between patients receiving standard and high-dose vancomycin in the IPTW analyses. No differences in recurrence, mortality or re-admission were identified between standard and high-dose vancomycin for the treatment of CDI not requiring surgery.