Pharmacodynamics I

Question 1

Know the similarities and differences between graded dose-response curves and quantal dose-response curves

Answer 1

Graded dose response curves allowus to characterize drug effects in an individual whereas quantal curves allowus to characterize those effects in a population by setting a set threshold.

Question 2

Know the differences between full and partial agonists.What is an inverse agonist?What is an antagonist?

Answer 2

Full agonist - an agonist that elicits a maximal responsePartial agonist - an agonists which elicits less than maximal responseInverse agonist - an agonist that decreases the activity of an occupied receptorAntagonist - binds to the receptor but elicits no reponse

Question 3

Know the similarities and differences between competitive antagonism and noncompetitive antagonism

Answer 3

• Competitive antagonist reversibly interacts with the same binding site as do agonists
• Non-competitive antagonists either bind irreversibly or bind at a different site than do agonists

Question 4

Understand why partial agonist can also function as competitive antagonists

Question 5

Know the definitions of the following: KD
Bmax
EC50 or ED50
Emax

Answer 5

KD= [L][R]/[LR], this equation tells us thatKDis the concentration of ligand when half of the receptors are bound to the ligand. Maximal binding is defined asBmax.

EC50 or ED50is the ligand concentration at which half maximal effect is observed. Similarly, concentration of ligand at which maxiaml effect is observed is defined asEmax

Question 6

What is KD a measure of?

Answer 6

It measures the tendency of ligand to bind to the receptors

Question 7

Define and contrast potency and efficacy.

Answer 7

Potency - concentration dependence of a drug’s effect, regardless of the magnitude of effectEfficacy - maximal effect elicited by a drug.

Question 8

What if KD and EC50 don’t match?

Answer 8

In such casesEC50is lower than KDso a half maximal effect can be achieved by a lower ligandconcentration. This can be explained by the presence of spare receptors.

Question 9

Explain the changes to the potency and efficacy of a drug in the presence of a competitive antgonist.

Answer 9

The potency decreases, the efficacy however remains the same.

Question 10

Explain the changes to the potency and efficacy of a drug in the presence of a noncompetitive antgonist.

Answer 10

Efficacy and potency both are reduced.