Ceftazidime-avibactam (CAZ-AVI) is a novel intravenous b-lactam/b-lactamase inhibitor combination used in the treatment of multidrug-resistant (MDR) gram-negative infections. Although renal dosing recommendations exist for the medication, limited data are available for dosing in patients receiving continuous renal replacement therapy. In this report, we describe a case in which CAZ-AVI 2.5 g was administered as a 2-hour infusion every 8 hours to a 50-year-old critically ill patient with MDR Pseudomonas aeruginosa (CAZ-AVI minimum inhibitory concentration [MIC] 8 lg/ml) pneumonia who was also receiving continuous venovenous hemodiafiltration (CVVHDF). Total serum concentrations of both ceftazidime and avibactam were measured at~0.5, 2, 4, and 6 hours after completion of the 2hour infusion of the 11th dose of CAZ-AVI. Ceftazidime pharmacokinetic parameters were as follows: maximum serum concentration (C max ) 152.39 lg/ml, half-life 5.17 hours, volume of distribution at steady state (Vd ss ) 11.51 L, clearance 1.54 L/hour, and area under the concentration-time curve (AUC) 1295.38 hour•lg/ml. This regimen achieved free ceftazidime serum concentrations more than 4 times the MIC for 100% of the dosing interval. Avibactam pharmacokinetic parameters were as follows: C max 35.83 lg/ml, half-life 5.92 hours, Vd ss 12.44 L, clearance 1.45 L/hour, and AUC 343.44 hour•lg/ml, which achieved free avibactam concentrations above 1 lg/ml for 100% of the dosing interval. Higher Institutional review board and funding source: For this work, a medication approved by the Food and Drug Administration was used in the course of routine medical care and was considered exempted research (https://www.hhs.gov/ohrp/regulationsand-policy/decision-charts/index.html#c1). Drug concentrations were not used to alter medical management of the patient and were not reported until after the patient was discharged from our facility. Drug concentrations were paid for by a pharmacy department research and education fund and were not charged to the patient.