Pharmacokinetic–Pharmacodynamic Relationship: Exposure, Response and Effect

The pharmacokinetic–pharmacodynamic relationship links the body’s drug exposure to its efficacy and toxicity, leading to an optimal drug dosing regimen.

It uses mathematical modeling to define the drug concentration-effect relationship through drug exposure, response, and effect.

Exposure, a pharmacokinetic characteristic, indicates the drug amount that causes a response. It can be measured by drug dose or plasma concentrations.

Response reflects the observable drug’s pharmacological effect, which may have a therapeutic or adverse outcome following post-drug exposure.

Lastly, an effect is the quantifiable alteration in a biological parameter over time.

It includes biomarkers from indirect indicators like receptor occupancy, mechanistic indicators such as percent ACE inhibition, and potential surrogate markers such as variations in baseline blood pressure.

For example, before dosing, the baseline diastolic blood pressure or DBP is 92 mm Hg and after 8 weeks of therapy, the DBP drops to 82 mm Hg, then the effect is a 10 mm Hg reduction.