What %T>MIC target is required for beta-lactam efficacy?

Bacteriostatic effect requires 30-40% T>MIC; bactericidal effect requires 50-70% T>MIC; optimal outcomes in severe infections require >90-100% T>MIC for serious gram-negative infections.

How does extended infusion of meropenem improve pharmacodynamics?

Meropenem 2g over 3h vs 0.5h infusion doubles the time plasma exceeds MIC, enabling bactericidal coverage against organisms with MIC 2-8 mcg/mL that would be missed by standard 0.5h infusions.

Is there a stability limit for continuous beta-lactam infusion?

Piperacillin-tazobactam is stable 12h at room temperature; meropenem only 3-4h (change bags frequently); cefepime 12h; ceftriaxone stable 24h; stability is the main practical limitation for continuous infusion.

When is continuous infusion superior to intermittent dosing?

Continuous infusion benefits: organisms with MIC near breakpoint (resistant/heteroresistant), critically ill with altered Vd and clearance, documented treatment failures on standard regimens, high inoculum infections.

What is the advantage of high-dose extended carbapenem for NDM producers?

For NDM and KPC Klebsiella with MIC 2-8 mg/L, extended infusion meropenem 2g q8h over 3h can achieve >90% T>MIC; combination with novel beta-lactamase inhibitors (ceftazidime-avibactam) is preferred for MIC >8.

Beta-Lactam Extended/Continuous Infusion Pharmacodynamics

Calculates optimal beta-lactam dosing using %T>MIC target attainment for piperacillin-tazobactam, meropenem, and cefepime extended or continuous infusions in severe infections with resistant organisms.

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