Pharmacodynamics

Question 1

what is the law of mass action?

Answer 1

Ligands bind reversibly to their receptors therefore the process is an equilibrium. You add more ligand, more binding occurs, the ligand receptor complexes there are, the equilibrium shifts to the left and less binding occurs.

Question 2

How is affinity of a ligand for its receptor measured?

Answer 2

Kd- this is the dissociation constant- and is the concentration of drug where 50% of the receptors are occupied

Question 3

What is the intrinsic efficacy of antagonists compared to agonists?

Answer 3

Trick question- antagonists have no intrinsic efficiacy, so just sit there in the receptor and stop agonists getting through.

Question 4

What is efficacy?

Answer 4

The ability of a ligand to cause a response. It is governed by intrinsic efficacy + cell factors.

Question 5

What is Bmax?

Answer 5

The maximum number of occupied receptors

Question 6

What is EC50?

Answer 6

The effective concentration giving 50% of the maximal response. This is the same as POTENCY.

Question 7

In what situations would receptor occupancy not be 100% when response is 100%?

Answer 7

When there are spare receptors