1622 - Outcomes of Colistin Weight-Based Dosing Versus The Non-Weight-Based Dosing

Background: The use of colistin is currently the mainstay antimicrobial for several multi-drug resistant organisms (MDROs). New guidelines were recently published recommending non-weight-based (NWB) dosing of colistin.  There is limited data on outcomes with this new dosing strategy. The purpose of this study was to investigate the outcomes of the new NWB dosing strategy in comparison to the previously used weight-based (WB) dosing strategy.

Methods: A retrospective study was conducted at our quaternary care hospital between January 2016 and April 2020. Adults (≥ 18 years), who received intravenous (IV) colistin for ≥ 72 hours were included. Documented clinical cure was the primary endpoint, which was defined as having at least two of the following: normalization of white blood cell count or ≥ 25% reduction, defervescence, hemodynamic stability, normalization of inflammatory markers (C-reactive protein and procalcitonin values) or ≥ 25% reduction, or the resolution of signs and symptoms of infection by the end of the therapy. Secondary outcomes were microbiological cure, incidence of acute kidney injury (AKI), time to AKI, outcomes of AKI, time to AKI recovery, new infection while on IV colistin, recurrence of infection, and all-cause mortality.

Results: A total of 104 primarily male (57.7%) patients with a mean age of 63 ± 20.23 years and weight of 70.24 ± 19.46 kg met the inclusion criteria. At baseline for both groups, the estimated creatinine clearance was 74.23 ± 70.86 mL/min and renal replacement therapy was observed in 34.62%. There was no statistically significant difference observed in clinical cure rate in the WB was 77.03% while 83.33% in the NWB (p-value 0.48). However, a higher rate of AKI was observed in NWB was 84.21% while 53.33% in WB (p-value 0.02). Amongst those who had AKI, NWB had better AKI recovery status with 60.00% while 17.95% in WB (p-value 0.00). A higher all-cause mortality rate was observed in the WB group with 55.41% while 20.00% in NWB (p-value 0.02).

Conclusion: The study showed no statistical difference in the primary outcome between the two groups, however, higher AKI rates, AKI recovery and all-cause mortality was observed in non-weight-based dosing when compared to the weight-based dosing. Our data needs to be validated in a larger study.