Main Body

11. Types of Drug-Drug Interactions

Additivity: when the effect of two drugs given in combination equals the mathematical summation of their effects when given alone.

Synergism: when the combine effect of two drugs is greater than the sum of their effects when given separately.

Potentiation: when one drug does not elicit a response on its own but enhances the response to another drug.

Examples of Drug-Drug Interactions: given responses to 4 drugs

  • Drug A = 0 units response
  • Drug B = 3 units response
  • Drug C = 5 units response
  • Drug D = 10 units response

See Below
Drug A + Drug B = 5 units >> potentiation
Drug B + Drug C = 8 unites >> additivity
Drug C + Drug D = 20 units >> synergism

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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.