A descriptive pharmacokinetic/pharmacodynamic analysis of continuous infusion ceftazidime-avibactam for treating DTR gram-negative infections in a case series of critically ill patients undergoing continuous veno-venous haemodiafiltration (CVVHDF)

Purpose: To explore pharmacokinetic/pharmacodynamic (PK/PD) profile of continuous infusion (CI) ceftazidime-avibactam for treating difficult-to-treat resistant Gram-negative (DTR-GN) infections in critical patients undergoing continuous venovenous haemodiafiltration (CVVHDF). Materials and methods: Patients treated with CI ceftazidime-avibactam for DTR-GN infections during CVVHDF were retrospectively assessed. Ceftazidime and avibactam concentrations were measured at steady-state and the free fraction (fCss) was calculated. Total clearance (CLtot) of both agents were calculated and the impact of CVVHDF intensity was assessed by linear regression. The joint PK/PD target of ceftazidime-avibactam was defined as optimal when both fCss/MIC≥4 for ceftazidime and fCss/CT > 1 for avibactam were achieved. Relationship between ceftazidime-avibactam PK/PD targets and microbiological outcome was assessed. Results: Eight patients with DTR-GN infections were retrieved. Median fCss were 84.5 (73.7–87.7 mg/L) for ceftazidime and 24.8 mg/L (20.7–25.8 mg/L) for avibactam. Median CLtot was 2.39 L/h (2.05–2.96 L/h) for ceftazidime and 2.56 L/h (2.12–2.98 L/h) for avibactam. Median CVVHDF dose was 38.6 mL/h/kg (35.9–40.0 mL/kg/h). CLtot were linearly correlated with CVVHDF dose (r = 0.53;p = 0.03, and r = 0.64;p = 0.006, respectively). The joint PK/PD targets were optimal granting microbiological eradication in all the assessable cases. Conclusion: CI administration of 1.25–2.5 g q8h ceftazidime-avibactam may allow prompt attainment and maintenance of optimal joint PK/PD targets during high-intensity CVVHDF.