187Colistin and its Effect on Renal Function: A Retrospective Review at an Urban Hospital

Background. The emergence of multi-drug resistant gram negative organisms has led to the frequent use of colistin, an antibiotic first available for clinical use in 1959 but unpopular due to concerns of renal failure. Recent literature suggests colistin nephrotoxicity may be overestimated. Aggressive, weight based dosing with an initial loading dose is recommended for colistin therapy in our institution. We completed a retrospective analysis to assess the utilization of a colistin dosing protocol and its effect on renal injury in an urban academic hospital. Methods. All patients admitted to University Hospital who received colistin between 2010 and 2013 were reviewed retrospectively. 144 patients were identified and data abstracted included patient demographics, colistin doses, serum creatinine, use of renal replacement therapy and hospital disposition. Dosages given were compared to hospital guidelines and renal clearance (based on Cr clearance) was utilized as a measure of renal failure. Acute kidney injury (AKI) was defined as a change in creatinine greater than 0.5 mg/dL from baseline. Results. Onmany occasions, colistin was not appropriately dosed. The loading dose of colistin was given correctly to 70 patients (48.61%) whereas it was not given in 70 patients and overdosed in 4 patients (2.78%). There were 1170 maintenance doses given in total: 610 correct doses (52.14%), 158 overdoses (13.50%) and 402 underdoses (34.36%). Renal function was monitored throughout hospitalization. There were only 34 patients (23.61%) who met criteria for AKI prior to start of colistin, whereas 76 patients (52.77%) met criteria for AKI after starting colistin. Additionally, there was a greater rise in creatinine with more adherence to the colistin dosage protocol. On average, there was a change in Cr of 1.72 mg/dL when colistin was dosed correctly 75-100% of the time as opposed to a change in Cr of 0.73 mg/dL when dosed correctly only 0-25% of the time. Conclusion. Colistin is being inappropriately under-dosed as per hospital protocol approximately 50%of the time in regards to loading doses and maintenance doses. However, we still see considerable acute kidney injury, especially when adhering to hospital protocol, which contrasts with the latest literature that claims the nephrotoxic effects of colistin to be overestimated. Disclosures. All authors: No reported disclosures.