PK/PD in Clinical Practice

Multi-drug resistance gram-negative rods (CDC)

There is a great article in the November 1st issue of Clinical Infectious Diseases where Labreche and colleagues discuss recent updates on using pharmacokinetics-pharmacodynamics (PK/PD) in antimicrobial susceptibility testing.

Given the current crisis of gram-negative resistance and the paucity of new drugs in development it is critical that physicians learn to optimize their use of the drugs left in our armamentarium. For most antibiotics/ organisms susceptibility results are simply listed as "S"usceptible, "I"ntermediate, or "R"esistant. Oftentimes the Minimum Inhibitory Concentration (MIC) of the organism is not provided; even when these values are provided they are difficult for most physicians to interpret. What is needed is a better understanding of PK/PD principles as well as how to navigate the complex recommendations of the many organizations providing antibiotic susceptibility cutoffs.

Labreche and colleagues provide a nice overview of core PK/PD principles and also discuss the different agencies that provide breakpoints for different organisms and drugs (FDA, CLSI, EUCAST). For the latter, differences in how the organizations come up with recommendations are highlighted. Several useful examples of recent changes are provided and how these changes can be applied to clinical practice.