4, 9/8 Agonists and Antagonists

Exam 1, Lecture 22

What is affinity

The tendency of a drug to combine with the respective receptor

What does affinity depend on

Chemical structure of the drug

What does a strong binding force mean

Long term intercation with the receptor

How is affinity measured

dissociation constant Kd

What does Kd Measure

50% occupancy of receptors

how are Kd and affinity related?

directly

What is the difference between intrinisc efficacy and efficacy

Intrinsic efficacy is about the receptor drug complex

What is intrinsic efficacy

Maximum effect the drug can produce

What does intrinsic efficacy depend on

Drug structure and drug receptor complex

between affinity and intrinsic efficacy, what is not present in an antagonist

Antagonist only has affinity, no intrinsic efficacy

What are the two types of agonists?

Primary and allosteric

What is a primary agonist

Drug that binds to the same site as the endogenous ligand

what is an allosteric agonist

Drug binds to a different region of the receptor

What is a full agonist

produces the maximum effect

What is an example of a full agonist

Norepenipherine and epinephrine

What is a partial agonist

Produces a sub optimal response

Which number changes with a partial agonist

Emax, the maximum effect

what are the 3 types of antagonism by drugs

Receptor, physiological, and chemical

What is physiological antagonism

Drugs affect different physiological areas, parasympathetic vs sympathetic

WHat is chemical antagonism

acid vs alkali drugs

Can drugs act as agonists and antagonists on different receptors

no, only opioids

What is competitive antagonism

Antagonist acts on same receptor as agonist

is competitive antagonism reversible or irreversible, how

reversible, with enough concentration

how does competitive antagonism affect efficacy/Emax

remains the same

how does competitive antagonism affect potency

decreases

how does competitive antagonism affect Ec50

Increases

How is the graph changed with competitive antagonism

same height and starting point, but less steep curve, EC50 moved to right

Is noncompetitive antagonism reversible or irreversible, how

Irreversible, the binding site changes shape

How does noncompetitive antagonism affect efficacy

decreases

How does noncompetitive antagonism affect EC50

Increases

How does noncompetitive antagonism affect potency

decreases

How does the graph change for non competitive antagonism

Starting point to the right, ending point not as high, same slope

What kind of receptors can have an inverse agonist

Ones with basal level of activity

What does an inverse agonist do

produces an opposite pharmacological effect

What is an example of an inverse agonist

Histamine

When is the response of a drug terminated

When the drug dissociates from the receptor

What are the three sections of a dose response curve

No effect range, range with increasing effect with increasing dose, maximum effect range

What does a narrow therapeutic window mean

Closer values of clinical efficacy and toxic dose, more possibility for drug toxicity

What is a graded dose response relationship

drug that has an effect that increases proportionately to an increase in the dose

What is a quantal dose response relationship

drug is observed in a population as either having an effect or not having an effect