Quantative Pharmacology

• Agonist or antagonist is

  • Non-covalent
  • Usually reversible
  • Competitive (only one binding site for agonists and antagonists)
  • Specific - may be non specific binding to non-receptor sites or non-ligand binding domains
  • Selective - drugs bind only to a restricted population of receptors
• Rate of Dissociation

  • Number of molecules dissociating per second
  • Proportional to the concentration of receptor-ligand complex (more complexes, more ligands dissociating)
  • Rate constant is fraction of [RL] from which ligand dissociates per second
• Rate

  • is the number of molecules (expressed as a

  concentration)associating per second

  • is proportional to the concentration of

  receptor and ligand

  – Rate constant (kon)

  • is simply a number relating the rate to the

  concentration of receptor and ligand

  complex
• $f=$$\frac{\left[RL\right]}{\left[R\right]t}=$\frac{\left[L\right]}{\left[L\right]+Kd}

  Fractional Occupancy
• $\frac{E}{E\ \max}=$\ \frac{\left[D\right]}{\left[D\right]\ +EC50}