Drug Binding

Question 1

Bmax

Answer 1

Binding capacity or total receptor binding

Question 2

Kd

Answer 2

Dissociation constant; the concentration of ligand required for 50% of receptors to be occupied

A larger Kd indicates that the drug has a LOWER affinity for its target

Question 3

Measuring drug binding

Answer 3

Binding of drugs to receptors can be measured directly using radioactive labels

However, this is often some non-specific binding in these experiments

To calculate the level of non-specific binding, a non-radioactive molecule that completes saturates the receptor is added

Non specific binding can then be subtracted from total binding to find non-specific binding

Question 4

EC50

Answer 4

Effective concentration 50

The concentration of drug required to elicit half a maximal response from the tissue

Question 5

ED50

Answer 5

Effective dose 50

The dose of drug required to elicit half a maximal response from the tissue

Question 6

Efficacy

Answer 6

The ability of a drug to elicit a response from its target

Antagonists do not have efficacy because do not cause a response from their target

Question 7

Selectivity

Answer 7

The ability of a drug to bind to a multiple receptors

Question 8

Affinity

Answer 8

The ability of a drug to bind to a specific receptor

Measured as a Kd value

Question 9

Agonist

Answer 9

Has both affinity for the target and efficacy at the target

Partial agonists are unable to generate a maximal response from the tissue

Question 10

Antagonist

Answer 10

Has affinity for the target, but no efficacy at the target

Antagonist activity can be measured by comparing the efficacy of a corresponding agonist before and after the addition of the antagonist

Reversible antagonists can be out-competed by the endogenous substrate