Drug Targets Drug A Receptor R complex AR regulates cellular function Quantum All or None Response Therapeutic Index Graded Dose Response Curve Drug Targets Kd Equilibrium Dissociation constant unit M Kd k2 k1 R D k1 RD k3 Effect k2 Low Kd high affinity difficult to dissociate nM to pM High Kd low affinity quick to dissociate mM to M fb D Kd D Dose Response Curve Occupational Theory of Drug action In occupational theory of drug action fraction of receptor binding is equal to the fraction of max effect However it was demonstrated later that the occupational theory does not work in most of cases Response is not proportional to the fraction of receptor occupancy 100 binding is not necessary to generate max response 1 2 Signal is amplified at the receptor The concept of spare receptors Potency and Efficacy are independent Agonist and Antagonist Antagonist Competitive or Noncompetitive Competitive Antagonist and Noncompetitive antagonist Partial Agonist Potency and Efficacy Allosteric Theory of Drug action Inverse Agonist Allosteric Theory two state theory of drug action Response is not proportional to the fraction of receptor occupancy 100 binding is not necessary to generate max response 1 2 Signal is amplified at the receptor The concept of spare receptors Response is amplified at the membrane
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