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Int J Antimicrob Agents. 2007 Mar;29(3):341-3. Epub 2007 Jan 16.

Is all free time above the minimum inhibitory concentration the same: implications for beta-lactam in vivo modelling.

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Center for Anti-Infective Research and Development, Hartford Hospital, 80 Seymour Street, Hartford, CT 06102, USA.


Previously, ertapenem 50 mg/kg every 6h given subcutaneously to mice achieved a similar 24-h cumulative free time above the minimum inhibitory concentration (fT>MIC) to 1g every 24h in humans. However, this simplified regimen (SR) does not provide a superimposable concentration-time profile to that observed in humans, thus allowing concentrations to fluctuate above and below the minimum inhibitory concentration (MIC) throughout the 24-h period. Herein, we compared a complex regimen (CR; 9 various mg/kg doses over 24 h) providing a near superimposable concentration-time profile with the SR to determine implications on bacterial kill against eight extended-spectrum beta-lactamase (ESBL)-producing isolates over a wide MIC range. The CR resulted in a similar (+/-5%) 24-h cumulative fT>MIC to ertapenem 1 g every 24h in humans over an MIC range of 0.032 mg/L to 16 mg/L. Similar bacterial kill was observed with both regimens against all eight ESBL-producing isolates examined. In mouse models, it appears that the 24-h cumulative fT>MIC and not the distribution of the fT>MIC over 24 h drives efficacy.

[Indexed for MEDLINE]

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