Learning Objective

To understand how the body handles drugs through the core pharmacokinetic processes of absorption, distribution, metabolism, and excretion (ADME), and to recognize how drug permeation across biological membranes influences overall biodisposition and clinical outcomes.

Pharmacokinetics

Pharmacokinetics describes what the body does to the drug. It includes four major processes collectively known as ADME:

A — Absorption

The entry of the drug from the site of administration into the bloodstream.

D — Distribution

Reversible movement of the drug between the blood and tissues.

M — Metabolism (Biotransformation)

Chemical alteration of the drug, primarily by enzymes (mainly hepatic), to increase water solubility for elimination.

E — Excretion

Removal of the drug and its metabolites from the body, mainly via kidneys (urine), liver (bile), lungs, or other pathways.

Activity