Aim for Cmax:MIC ratio of 10-12.

As concentration-dependent antibacterials, the efficacy of fluoroquinolones has been shown to correlate with the ratio of the peak serum concentration to the MIC of the organism (Cmax:MIC), as well as the ratio of the 24 hour area under the plasma concentration curve (AUC₂₄:MIC). Optimizing the AUC₂₄/MIC ratio can result in better clinical outcomes and limit the development of resistance.  Various AUC₂₄/MIC target ratios have been proposed in the literature but no firm recommendations can be made as these ratios are dependent on multiple factors including:

- antibiotic

• total vs free drug concentration (takes into account protein binding)
• bacteriostatic vs bactericidal activity

- organism

• Gram positive or Gram negative (higher AUC₂₄/MIC ratio generally required for Gram negative infections)
• MIC
• inoculum at site of infection

- immune status of the host (higher AUC₂₄/MIC ratio required in immuno-compromised patients).