Depending on the antimicrobial class, three relevant indices are traditionally described:
- the ratio of the (unbound) 24-h area under the curve to MIC (fAUC24/MIC);
- the ratio of the free maximal concentration to MIC (fCmax/MIC); and
- the time above the MIC expressed as a percentage of the dosing interval (f%T>MIC).
The magnitude for a PK/PD index describes at which level a required response is achieved.
It helps to design dosing strategies to increase the probability of success of the antibiotic therapy, as well as minimize the side effects and the emergence of resistance.