Ceftazidime-avibactam: a novel cephalosporin/β-lactamase inhibitor combination.

Avibactam (formerly NXL104, AVE1330A) is a synthetic non-β-lactam, β-lactamase inhibitor that inhibits the activities of Ambler class A and C β-lactamases and some Ambler class D enzymes. This review summarizes the existing data published for ceftazidime-avibactam, including relevant chemistry, mechanisms of action and resistance, microbiology, pharmacokinetics, pharmacodynamics, and efficacy and safety data from animal and human trials. Although not a β-lactam, the chemical structure of avibactam closely resembles portions of the cephem bicyclic ring system, and avibactam has been shown to bond covalently to β-lactamases. Very little is known about the potential for avibactam to select for resistance. The addition of avibactam greatly (4-1024-fold minimum inhibitory concentration [MIC] reduction) improves the activity of ceftazidime versus most species of Enterobacteriaceae depending on the presence or absence of β-lactamase enzyme(s). Against Pseudomonas aeruginosa, the addition of avibactam also improves the activity of ceftazidime (fourfold MIC reduction). Limited data suggest that the addition of avibactam does not improve the activity of ceftazidime versus Acinetobacter species or most anaerobic bacteria (exceptions: Bacteroides fragilis, Clostridium perfringens, Prevotella spp. and Porphyromonas spp.). The pharmacokinetics of avibactam follow a two-compartment model and do not appear to be altered by the co-administration of ceftazidime. The maximum plasma drug concentration (C(max)) and area under the plasma concentration-time curve (AUC) of avibactam increase linearly with doses ranging from 50 mg to 2,000 mg. The mean volume of distribution and half-life of 22 L (0.3 L/kg) and ~2 hours, respectively, are similar to ceftazidime. Like ceftazidime, avibactam is primarily renally excreted, and clearance correlates with creatinine clearance. Pharmacodynamic data suggest that ceftazidime-avibactam is rapidly bactericidal versus β-lactamase-producing Gram-negative bacilli that are not inhibited by ceftazidime alone.Clinical trials to date have reported that ceftazidime-avibactam is as effective as standard carbapenem therapy in complicated intra-abdominal infection and complicated urinary tract infection, including infection caused by cephalosporin-resistant Gram-negative isolates. The safety and tolerability of ceftazidime-avibactam has been reported in three phase I pharmacokinetic studies and two phase II clinical studies. Ceftazidime-avibactam appears to be well tolerated in healthy subjects and hospitalized patients, with few serious drug-related treatment-emergent adverse events reported to date.In conclusion, avibactam serves to broaden the spectrum of ceftazidime versus ß-lactamase-producing Gram-negative bacilli. The exact roles for ceftazidime-avibactam will be defined by efficacy and safety data from further clinical trials. Potential future roles for ceftazidime-avibactam include the treatment of suspected or documented infections caused by resistant Gram-negative-bacilli producing extended-spectrum ß-lactamase (ESBL), Klebsiella pneumoniae carbapenemases (KPCs) and/or AmpC ß-lactamases. In addition, ceftazidime-avibactam may be used in combination (with metronidazole) for suspected polymicrobial infections. Finally, the increased activity of ceftazidime-avibactam versus P. aeruginosa may be of clinical benefit in patients with suspected or documented P. aeruginosa infections.