Article Sections

Introduction

Pharmacodynamics (PD) and pharmacokinetics (PK) are the foundations of pharmacology:

  • PK (what the body does to the drug) involves absorption, distribution, metabolism, and excretion (ADME), which influence properties such as bioavailability, volume of distribution, half-life, clearance, and steady-state concentration.  PK determines the drug concentration at the site of action.
  • PD (what the drug does to the body) involves drug-receptor behavior (agonism, antagonism), dose-response curves, therapeutic indices, and desensitization phenomena such as tolerance and tachyphylaxis.

This article covers the major aspects of PD.

Agonists

Drugs act on various receptor types, including G protein–coupled receptors (GPCRs) ( Figure 1), ion channels ( Figure 2), tyrosine kinases ( Figure 3), nuclear hormone receptors ( Figure 4), and enzymes.  These receptor signaling systems are discussed in more detail in a separate article.

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Figures

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