Pharmacodynamics of Antimicrobials

Pharmacodynamic parameters predictive of outcome for the various classes of antimicrobials:

T > MIC

T > MIC = time that the free drug concentration is above the MIC

MIC = minimum inhibitory concentration

Time-dependent antibacterial activity; dosing should aim to maximize time that the free drug concentration is above the MIC of the pathogen(s)

Penicillins
Cephalosporins
Carbapenems
Aztreonam
Erythromycin
Flucytosine

Fosfomycin (vs S. aureus, P. aeruginosa)

Cmax:MIC

Cmax = peak free drug concentration

MIC = minimum inhibitory concentration

Concentration-dependent antibacterial activity; dosing should aim to achieve high peak serum drug concentration relative to the MIC of the pathogen(s), e.g. extended-interval AG dosing

Aminoglycosides (AG)
Fluoroquinolones

Fosfomycin (vs S. aureus, S. pneumoniae, E. faecium, E. coli, P. mirabilis)

Metronidazole (vs anaerobes)
Amphotericin B
Daptomycin
Anidulafungin
Caspofungin
Micafungin

AUC₂₄:MIC

AUC₂₄ = 24h area under the free drug concentration-time curve

MIC = minimum inhibitory concentration

Concentration-dependent with time dependence; dosing should aim to maximize amount of drug relative to the MIC of the pathogen(s); this can be achieved by increasing the dose and/or giving more frequently

Fluoroquinolones
Azithromycin
Clarithromycin
Clindamycin
Tetracyclines
Linezolid
Vancomycin
Tigecycline
Colistin
Fluconazole

Isavuconazole
Itraconazole
Posaconazole
Voriconazole