ABSTRACT
INTRODUCTION There has been a growing trend in the last 20 years to consider more and more the pharmacological activity of a drug in addition to its pharmacokinetic behavior. The pharmacological activity of a drug, its efficacy and toxicity, is commonly referred to as its pharmacodynamics (PD), while what is happening with its concentration time profile or its systemic exposure is referred to as its pharmacokinetics (PK). Another simple way of describing PK and PD is that the PK is what the body does to the drug (how it absorbs, distribute, and eliminates it), while PD is what the drug does to the body (how it decreases blood pressure, how it kills bacteria causing infections, etc.). For decades now, ever since the work of Shannon on antimicrobials (1), we know that PK and PD are linked. It is not enough to just discuss PK or PD separately but one needs to consider them together. Indeed, a fundamental principle of clinical pharmacology is that there is always a relationship between the concentrations of a drug at its sites of efficacy and/or toxicity and its efficacy and/or toxicity.
