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Flashcards in DRUG TARGETS 1 Deck (18):

Explain affinity?

Affinity is the attraction of a ligand(drug) for its receptor (shapes, charges)


Explain efficacy?

Tendency of the drug once bound, to activate the receptor is called efficacy. Maximum effect=1 Minimum effect=0


Explain specificity?

Specificity means that the drug can only bind to one receptor type.Weak affinities for everything else which can cause unwanted side effects.


Explain selectivity?

Preferential binding to a certain subtype(of a receptor family) leads to a greater effect at that subtype than others.
-eg salbutamol at B2(lungs) rather than B1(heart)
-Selectivity for H1 receptors is how current antihistamines work.
-Chemotherapy is designed to be selective for cells/organisms it is targeting.


Explain the receptor occupancy theory?

Drug effect is proportional to the number of receptors occupied.


Explain the rate theory?

Drug effect is proportional to the rate of occupancy


Explain the floating receptor model?

the D-R complex may interact with a variety of effectors in the membrane to produce its effect.


Explain the two state model?

the receptors exist in active or inactive form


What is the symbol for Inactive form?



What is the symbol for the active state?



Describe what happens to the equilibrium in the 2-state model when no ligand is bound?

Equilibrium favours R(inactive state)


What is an agonist?

A drug which binds and activates the receptor.


Describe what happens to the 2-state model with the full agonist?

Full agonist- efficacy of 1
Equilibrium strongly shifted to R*(active state)


Describe what happens to the 2-state model with the partial agonist?

Efficacy between 0 and 1.
Equilibrium partially shifted to R*(active state) ie there is a weak preference for R*


Describe what happens to the 2-state model with an inverse agonist?

The inverse agonist has a higher affinity for R than R* and so shifts the equilibrium to the left.


What is an antagonist?

A drug which binds to the receptor without causing activation but prevents the agonist from binding.


Describe what happens to the 2-state model with an antagonist?

Efficacy of 0
No preference for either state
Equilibrium not shifted.


What is the term receptor plasticity referred to?

Receptor states and populations are never constant. Thus plasticity refers to the changes in effectiveness of the drug over time in response to these changes in receptor populations.