Main Body

6. Characteristics of Drug-Receptor Interactions:

  1. Follow Mass-Action Law: rate of reaction is DIRECTLY proportional to the concentration of the reactants, however, there is a limit. This limit is called the point of saturation
    • There are only so many receptors on each cell to which a drug can bind. Point of saturation refers to the point at which every receptor is bound.
  2. Selectivity: every drug has a preferred receptor; however, it may bind to others with the same or lesser affinity than its preferred receptor. Side effects of drugs are a direct result of low selectivity because one drug can bind multiple receptors producing undesired biological responses.
    • Not to be confused with “specificity” meaning drug can only bind to one type of receptor, regardless of the drug dose: drugs that are “specific” are unheard of at this point
  3. Response is Proportional to Drug Dose [Concentration] up to the point of saturation
  4. Binding Changes the Receptor: when a drug binds a receptor it results in one of two changes as outlined below:
    • AGONIST: results in an active receptor conformation to produce desired biological effect, i.e. intracellular signaling or changes in organ function
  5. ANTAGONIST: a simple occupancy by the antagonist of the receptor to hinder access of an agonist to its binding site on the receptor, therefore, obliterating the response to the agonist.


Icon for the Creative Commons Attribution-NonCommercial 4.0 International License

Principles of Pharmacology - Study Guide Copyright © by Edited by Dr. Esam El-Fakahany and Becky Merkey, MEd is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License, except where otherwise noted.