Antimicrobial agents work by killing or preventing the growth of a microorganism whilst having little or no impact on the host. Antimicrobials include agents that act against all types of microorganisms: bacteria (anti-bacterial), viruses (anti-viral), fungi (anti-fungal) and protozoa (antiprotozoal). Dosing regimens of antimicrobials should be optimised to prevent or minimise resistance. Suboptimal dosing has been attributed to poorer clinical outcomes and cure rates, as well as increasing the risk of morbidity and mortality.  

Pharmacokinetics (PK) is the study of the time course of drug absorption, distribution, metabolism and elimination i.e. what the body does to a drug. Pharmacodynamics (PD) is the study of the relationship between drug concentration at the site of action and the resulting effect i.e. what the drug does to the body. 

Target PK* and PD* indices are crucial to achieving maximal antibiotic activity and effective treatment of infection. However, adequate antimicrobial dosing to achieve PK/PD targets remains a challenge. The administered drug doses are frequently obtained from data from healthy individuals and often do not account for PK/PD differences in different patient populations, such as septic patients. Thus, optimising antimicrobial dosing regimens requires robust knowledge of the pharmacokinetics and pharmacodynamics of the antimicrobial agent. 

It should be noted that PK/PD principles relate to all drugs but for the purpose of this eModule the focus being on antimicrobial agents.