Unit 2 - Pharmacodynamics, AAEPA, Dose Response Curve, Window

Question 1

What is affinity?

Answer 1

Strength of the binding between a drug and its receptor

Question 2

What is efficacy?

Answer 2

The ability of a drug to elicit the maximal biological effect.

Determined mainly by the nature of the drug and receptor and its associated effector system.

Can be measured with a graded dose-response curve - not with a quantal dose-response curve.

Question 3

What is potency?

Answer 3

Denotes the amount of drug needed to produce a specified effect.

On a dose-response curve, the drug that has the lowest EC50 is the most potent.

ED50 is the dose at which 50% of the popuation or sample manifests a given effect; used with quantal graphs

Measure of potency is effective dose to treat 50% of people

Question 4

What is Kd?

Answer 4

the ratio of breakdown

Kd = K-1/K1

Question 5

What is K1?

Answer 5

Rate of binding/attachment

Question 6

What is Ki?

Question 7

Give some examples of sites of drug action

Answer 7

enzymes, ion channels, neurotransmitter transport systems, nucleic acids, receptors

Question 8

What is a receptor?

Answer 8

Specific chemical constituent of the cell with which a drug interacts to produce its pharmacological effects.

Normally a protein or glycoprotein that sits on the cell surface.

Question 9

What are the 2 forms of receptors?

Answer 9

Active Ra and Inactive Ri

Question 10

What is a second messenger?

Answer 10

Molecules that convey messages from the first messenger to the target organ.

Effect of drug can only happen after the drug binds to the receptor.

Question 11

Which of the following is responsible for selectivity of drug action?

A. Receptor
B. Second messenger
C. Neurotransmitter

Answer 11

A. Receptor

Question 12

What do receptors mediate?

Answer 12

Pharmacological agonists and antagonists

Question 13

When a drug binds to its receptor, it forms a…

Answer 13

drug-receptor complex

Question 14

Low affinity

Answer 14

slow formation and rapid breakdown

Question 15

High affinity

Answer 15

Rapid formation and slow breakdown

Question 16

What is K-1?

Answer 16

Rate of letting go/breakdown

Question 17

Drugs with a high rate of dissociation (K-1) and a low rate of formation (K1) will have a ______ dissociation constant

Answer 17

High - drug does not bind well to its receptor

Question 18

Drugs with a low rate of dissociation (K-1) and high rate of formation (K1) will have a _____ dissociation constant

Answer 18

low - binding of drug and receptor is strong

Question 19

What is a ligand?

Answer 19

something that binds to a receptor site on a target protein

Question 20

ED50

Answer 20

Effective dose of drug to treat 50% of people

Question 21

What does an antagonist do at the organism level?

Answer 21

Bind to same site as the endogenous ligand but do not produce the same signal as the endogenous ligand.

Question 22

What is reversible antagonism?

Answer 22

Competitive (antagonist binds to same site as agonist in a reversible manner - potency affected, not efficacy) and non-competitive (binds to site other than receptor for agonist, yet keeps the agonist from having an effect - reduces maximal response that an agonist can produce; efficacy and potency affected)

Question 23

What is irreversible antagonism?

Answer 23

binds to same site but with very high affinity; dangerous; dissociates slowly or not at all from receptor

Maximal efficacy reduced, no change in agonist activity at unoccupied receptors

Dose-response curve shifts to the right

Question 24

What is physiological antagonism?

Answer 24

actions of a substance that counteracts the physiological effects of a drug

nothing to do with competition for receptor sites or binding sites

counteracts the physiological effects of the drug

Question 25

Acetylcholinesterase function

Answer 25

irreversible antagonist; role in hydrolysis and deactivation of acetylcholine - prevents acetylcholine reactivating receptor

Question 26

Quantal dose-response relationships

Answer 26

describes a drug effect which is binary (either present or absent)

Graphs plot the rate of an outcome occurrence in a population against the drug dose

Response or no response

Question 27

Therapeutic window

Answer 27

space or window between LD50 and ED50

Question 28

Therapeutic index

Answer 28

Ratio; measure of drug safety

drug with higher index is safer

Small window = low ratio

LD50/ED50

Question 29

Allosteric agonist, antagonist

Answer 29

a drug that binds to a receptor molecule without interfering with normal agonist binding but alters the response to the normal agonist.

Question 30

Chemical antagonist

Answer 30

Drug that counters the effects of another by binding the AGONIST drug (not the receptor)