FPI Dose Response Curves

Agonist

Drug which interacts with its receptors

Drug receptor complex generates a response

Size of response varies with

Proportion of receptors occupied

Proportion of receptors occupied varies with

Conc of agonist

Occupancy varies with

Agonist conc

What is measured instead of occupancy

Biological response

Dose response curve shows

Response against log10 agonist

Full agonist

Which elicit max response

Partial agonist

Which cannot produce maximal response

Why is not every agonist a full agonist

Characteristics of the tissue involved

Agonist receptor complex

Characteristics of the tissue involved

The total no of receptors present

Nature of receptor and response coupling

Agonist receptor complex

Intrinsic efficacy and is a property of the drug receptor complex

Affinity decreases

Dose response curve shifts further to the right

Efficacy increases

Max response that the agonist can produce also increases

Spare receptor hypothesis

To get a full response it is not always necessary for all receptors to be occupied, only a fraction of the total no. of the receptors

Spare receptors

More receptors present than are needed to generate the full response

Antagonist

Drug which reduces the response to another drug

Competitive antagonist

Interacts with same receptor as agonist

Types of competitive antagonists

Reversible competitive antagonists

Irreversible competitive antagonist

Reversible competitive antagonists

Effects can thus be reduced by adding more agonists

Antagonist dissociates from the receptor

Adding a reversible competitive antagonists

dose response curve shifts to the right along x-axis

Max response does not change

Irreversible competitive antagonist

Increasing conc has no effect

Antagonist does not dissociate from receptor

Adding an irreversible competitive antagonists

The curve does not shift

Max response decreases

Non-competitive Antagonism

Does not compete for the agonist receptors