ADME Concepts
Start with the big picture
Absorption is the movement of a drug from its administration site into the blood. Membrane permeability, ionization, formulation, and first-pass metabolism can affect how much reaches systemic circulation; bioavailability expresses that fraction. Distribution reflects movement between blood and tissues, shaped by factors such as blood flow, tissue and protein binding, and lipid solubility. Metabolism transforms drugs, commonly through Phase I reactions and Phase II conjugation, while excretion removes drugs or metabolites. The lesson also introduces pharmacokinetic parameters, including peak concentration and time to peak, volume of distribution, clearance, and half-life, as well as first-order and zero-order elimination. Together, these concepts provide a framework for understanding drug exposure and variability.
What you'll learn
- Describe the sequence and purpose of the four ADME processes.
- Identify factors that influence absorption and bioavailability.
- Explain how binding, barriers, and tissue uptake affect distribution.
- Distinguish Phase I metabolism from Phase II conjugation.
- Define key pharmacokinetic parameters and compare first- and zero-order kinetics.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
