Pharmacokinetics/pharmacodynamics of a β-lactam and β-lactamase inhibitor combination: a novel approach for aztreonam/avibactam.

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Pharmacokinetics/pharmacodynamics of a β-lactam and β-lactamase inhibitor combination: a novel approach for aztreonam/avibactam.

J Antimicrob Chemother. 2015 May 29;

Authors: Singh R, Kim A, Tanudra MA, Harris JJ, McLaughlin RE, Patey S, O'Donnell JP, Bradford PA, Eakin AE

Abstract
OBJECTIVES: The combination of aztreonam/avibactam has promising activity against MDR Gram-negative pathogens producing metallo-β-lactamases (MBLs), such as New Delhi MBL-1. Pharmacokinetic (PK)/pharmacodynamic (PD) understanding of this combination is critical for optimal clinical dose selection. This study focuses on the determination of an integrated PK/PD approach for aztreonam/avibactam across multiple clinical Enterobacteriaceae strains.
METHODS: Six clinical Enterobacteriaceae isolates expressing MBLs and ESBLs were studied in an in vitro hollow-fibre infection model (HFIM) using various dosing regimens simulating human-like PK for aztreonam/avibactam. The neutropenic murine thigh infection model was used for in vivo validation against two bacterial strains.
RESULTS: MIC values of aztreonam/avibactam for the isolates ranged from 0.125 to 8 mg/L. Using a constant infusion of avibactam at 4 mg/L, the aztreonam PK/PD index was observed as % fT>MIC. Studies performed in the presence of a fixed dose of aztreonam revealed that the efficacy of avibactam correlates best with percentage of time above a critical threshold concentration of 2-2.5 mg/L. These conclusions translated well to the efficacy observed in the murine thigh model, demonstrating in vivo validation of the in vitro PK/PD target.
CONCLUSIONS: PK/PD evaluations for aztreonam/avibactam in HFIM yielded a single target across strains with a wide MIC range. This integrated approach could be easily applied for forecasting clinically efficacious doses for β-lactam/β-lactamase inhibitor combinations.

PMID: 26024868 [PubMed - as supplied by publisher]