Core43: Principles of antimicrobial treatment - time-, concentration- and exposure-dependent antibiotics

⏱️ High-yield / 要点：Antibiotic efficacy depends on PK/PD pattern: time-dependent = T > MIC, concentration-dependent = Cmax/MIC, exposure-dependent = AUC/MIC.

Key concepts / 基本概念

• MIC / minimum inhibitory concentration = minimum drug concentration that inhibits visible growth of a specific microorganism.
• Antibiotic dosing should match the PK/PD driver of efficacy.
• Main patterns:
  • Time-dependent.
  • Concentration-dependent.
  • Exposure-dependent.

PK/PD patterns / PK/PDパターン

Type	Main PK/PD target	Clinical idea	Examples
Time-dependent	T > MIC	Keep drug concentration above MIC for enough time	β-lactams, macrolides, tetracyclines
Concentration-dependent	Cmax/MIC ± PAE	High peak concentration improves killing	Aminoglycosides, e.g. gentamicin
Exposure-dependent	AUC/MIC	Total drug exposure over time determines efficacy	Fluoroquinolones, colistin

Time-dependent antibiotics / 時間依存性

• Need drug concentration to remain above MIC for a sufficient portion of the dosing interval.
• Dosing interval should be frequent enough to maintain T > MIC and reduce resistance risk.
• Example:
  • Amoxicillin for otitis media/sinusitis often requires multiple daily doses.

Concentration-dependent antibiotics / 濃度依存性

• Killing improves when peak concentration is high relative to MIC.
• Often show PAE / post-antibiotic effect:
  • Bacterial growth remains suppressed even after drug concentration falls below MIC.
• Important parameters:
  • Cmax
  • AUC
  • PAE
• Example:
  • Gentamicin.

Exposure-dependent antibiotics / 曝露依存性

• Efficacy depends on total exposure over time.
• Main target: AUC/MIC ratio.
• Examples:
  • Ciprofloxacin / fluoroquinolones
  • Colistin

Remember / 覚え方

• Time-dependent = stay above MIC
• Concentration-dependent = high peak
• Exposure-dependent = total AUC