The highest concentration reached in the compartment of reference, usually plasma (see Cmax and plasma concentration), divided by the MIC.
Cmax/MIC is a PK/PD index that integrates PK (Cmax) and PD (MIC as a measure of potency).
If Cmax/MIC correlates best with outcome, a drug exhibits a concentration-dependent pattern of activity (e.g, the aminoglycosides, the fluoroquinolones, daptomycin, colistin, metronidazole). The amount of the drug rather than the dosing frequency determines the clinical efficacy. fCmax/MIC refers to the unbound fraction of the drug.
Pharmacokinetics and pharmacodynamics of antibacterial agents (Infectious Diseases Clinics of North America, 2009)
Reappraisal of contemporary pharmacokinetic and pharmacodynamic principles for informing aminoglycoside dosing (Pharmacotherapy, 2018)
Standardization of pharmacokinetic/pharmacodynamic (PK/PD) terminology for anti-infective drugs: an update (The Journal of Antimicrobial Chemotherapy, 2005)
The Role of PK/PD Analysis in the Development and Evaluation of Antimicrobials (Pharmaceutics, 2021)