Drug Absorption, Distribution, Metabolism, and Excretion (ADME)
Start with the big picture
Absorption is the transfer of a drug into systemic circulation and is described by bioavailability (F); permeability, degradation, and first-pass metabolism can reduce it. Distribution is reversible movement into tissues, summarized by volume of distribution (Vd), while protein binding and tissue barriers affect how much drug is available to act. Metabolism, mainly in the liver, includes Phase I reactions and Phase II conjugation; CYP450 enzymes may be induced or inhibited. Excretion contributes to drug removal. Clearance reflects elimination efficiency, and half-life relates Vd to clearance. The lesson connects these concepts with first-order and zero-order kinetics to explain how ADME influences drug disposition and dosing principles.
What you'll learn
- Describe the four stages of ADME and their influence on drug action.
- Explain bioavailability and factors that affect absorption.
- Interpret volume of distribution and the roles of protein binding and tissue barriers.
- Distinguish Phase I metabolism, Phase II conjugation, and CYP450 modulation.
- Relate clearance, half-life, and elimination kinetics to dosing principles.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
