- The drug binds to the receptor even at low doses 
- Stays bound for a longer period of time

High Binding Affinity 

- The drug needs higher doses to bind to receptors
- Binds for a shorter amount of time 

Low Binding Affinity 

- Different concentrations of low and high-affinity drugs


In the case of equal concentrations of low and high-affinity drugs: 
- High-affinity drug binds more to drug receptors than the low-affinity drug 
- High-affinity drug will be more potent if both drugs have an equivalent effect on receptors 

Mixed Affinity 

- Also called affinity 
- The attraction between a drug/ligand to a receptor 
- Drugs can have a high or low binding affinity for receptors

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- Binding affinity (where it binds to) and intrinsic activity (what it does) determines the action of a drug
- Drugs may bind strongly or weakly to receptors or not bind to any receptors at all 
- Drug molecules that affects more than one kind of receptor have more than one action in the body 
- Drugs exhibit dose response relationships 

Drug Action 

Breedlove, S. & Watson, N. (2017). Behavioral neuroscience, eighth edition. Oxford University Press.

Behavioral Neuroscience 8th Edition

Binding Affinity 

- Also called efficacy 
- The extent of a drug/ligand to activate a response after binding to a receptor 
- Agonists have high intrinsic activity 
- Antagonists have low intrinsic activity 
- Partial agonists have a middle response 

Intrinsic Activity

- Greater drug doses tend to produce greater effects
- This relationship is shown in dose-response curves

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