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J Antimicrob Chemother. 2011 Feb;66(2):343-9. doi: 10.1093/jac/dkq348. Epub 2010 Oct 5.

Pharmacodynamics of empirical antibiotic monotherapies for an intensive care unit (ICU) population based on Canadian surveillance data.

Author information

1
University of Manitoba, Winnipeg, Canada. zelenits@ms.umanitoba.ca

Abstract

OBJECTIVES:

To evaluate, using Monte Carlo simulation, the pharmacodynamics (PD) of empirical antibiotic monotherapies for serious infections consistent with Canadian intensive care unit (ICU) surveillance data.

METHODS:

Meropenem, piperacillin/tazobactam and cefepime, along with ceftobiprole, a broad-spectrum cephalosporin active against methicillin-resistant Staphylococcus aureus (MRSA), were tested at standard and highest recommended doses with and without prolonged infusion times (t'). Population pharmacokinetic models were used to simulate antibiotic serum concentrations (n = 5000). Cumulative target attainment (CTA) at >50%, >75% and 100% fT( > MIC) (percentage of time free concentrations exceed the MIC) targets were determined based on ICU surveillance data including 4798 pathogens, most commonly methicillin-susceptible S. aureus (20.1%), Escherichia coli (15.2%) and Pseudomonas aeruginosa (12.3%).

RESULTS:

With standard doses, ceftobiprole (500 mg every 8 h, t' 2 h) had 0.90 CTA at the >50% fT( > MIC) target while meropenem (1 g every 8 h, t' 0.5 h), piperacillin/tazobactam (3.375 g every 6 h, t' 0.5 h) and cefepime (2 g every 12 h, t' 0.5 h) reached >50% fT( > MIC) in 0.79-0.82 of the population (0.84-0.88 when MRSA was excluded). Piperacillin/tazobactam had the largest reduction in CTA at the >75% and 100% fT( > MIC) targets requiring prolonged infusions to maintain comparable PD. For all agents, prolonged infusions and/or high doses were required to achieve >0.9 CTA at the lowest target, to reach higher targets or to cover less susceptible pathogens such as P. aeruginosa.

CONCLUSIONS:

This study provides important comparative data on empirical antibiotic monotherapies in an ICU setting including preliminary data on ceftobiprole. Ceftobiprole was most active overall, but similar to meropenem, piperacillin/tazobactam (lowest target only) and cefepime when MRSA was excluded. Prolonged infusions in particular and high doses were effective at improving antibiotic PD.

PMID:
20926397
DOI:
10.1093/jac/dkq348
[Indexed for MEDLINE]

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