Pharmacodynamics and Drug Receptors

Question 1

What is pharmacodynamics?

Answer 1

• action of the drug on the body

- deals with the effects of drugs on biologic systems

Question 2

receptor

Answer 2

• molecule to which a drug binds to bring about a change in function of the biologic system

Question 3

receptor site

Answer 3

• specific region of the receptor molecule to which the drug binds

Question 4

inert binding molecule or site

Answer 4

• molecule to which a drug may bind without changing any function

Question 5

spare receptor

Answer 5

• receptor that does not bind drug when the [drug] is sufficient to produce maximal effect
• Kd> EC50
• receptor may not have a high enough affinity for the drug

Question 6

effector

Answer 6

• component that accomplishes the biologic effect after the receptor is activated by an agonist

Question 7

efficacy/ maximal efficacy (Emax)

Answer 7

• maximal effect that can be achieved with a particular drug, regardless of dose

Question 8

potentcy

Answer 8

• amount of drug needed to elicit desired effect/ produce a given effect

Question 9

How is potency determined?

Answer 9

• by the affinity of the receptor for the drug and the number of receptors available

Question 10

graded dose-response curve

Answer 10

• graph of increasing response to increasing [drug] or dose

Question 11

quantal dose-response curve

Answer 11

• graph of the fraction of a population that shows a specified response at progressively increasing doses

Question 12

EC50

Answer 12

• [ ] that causes 50% of the maximum effect or toxicity

Question 13

ED50

Answer 13

• dose that causes 50% of the maximum effect of toxicity

Question 14

TD50

Answer 14

• median toxic dose ([ ])

- dose ([ ]) at which toxicity occurs in 50% of cases

Question 15

LD50 (LC50)

Answer 15

• medial lethal dose ([ ])

- dose ([ ]) required to kill half the members of a tested population after a specified test duration

Question 16

Kd

Answer 16

• [drug] that binds 50% of the receptors in the system

Question 17

Bmax

Answer 17

• maximal number of receptors bound

Question 18

agonist

Answer 18

• drug that fully activates its receptor upon binding

Question 19

partial agonist

Answer 19

• drug that binds to its receptor but produces a smaller effect at full dosage than a full agonist
• less than full effect even when all the drug available is bound

Question 20

allosteric agonist

Answer 20

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

Question 21

antagonist

Answer 21

• pharmacologic antagonist that binds without activating its receptor and thereby prevents activation by an agonist

Question 22

competitive antagonist

Answer 22

• pharmacologic antagonist that can be overcome by increasing the concentration of agonist or affinity

Question 23

irreversible antagonist

Answer 23

• pharmacologic antagonist that cannot be overcome by increasing agonist concentration

Question 24

physiological antagonist

Answer 24

• drug that counter effects of another by binding to a different receptor and causing opposing effects

Question 25

chemical antagonist

Answer 25

- drug that counters effects of another by binding the agonist drug ( not the receptor)

Question 26

allosteric antagonist

Answer 26

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

Question 27

TI

Answer 27

- TD50: ED50

Question 28

signaling

Answer 28

- once an agonist drug has bound to its receptor, some effector mechanism is activated

Question 29

What is the classic drug-receptor interactions?

Answer 29

- drug is present in the extracellular space, effector mechanism resides inside the cell, and modifies some intracellular process - involves signaling across membranes

Question 30

How many types of signaling are there?

Answer 30

- 5

Question 31

What are the signaling types?

Answer 31

- diffusion - transmembrane receptors, outer and inner domain - receptor activates cytoplasmic tyrosine kinase molecules (JAKs) to P STATs - gated transmembrane channels - GPCR with coupling protein

Question 32

How are receptors regulated?

Answer 32

- dynamic | - number, location, and sensitivity

Question 33

How are receptors changed?

Answer 33

- over time

Question 34

tachyphylaxis

Answer 34

- acute decrease in the response to a drug after its administration

Question 35

What causes tachyphylaxis?

Answer 35

-frequent or continuous exposure to agonists, resulting in short-term reduction of receptor response

Question 36

downregulation

Answer 36

- long-term reduction in receptor number which occur in response to continuous exposure to agonists

Question 37

upregulation

Answer 37

- increases in receptor number which occur when receptor activation is blocked for prolonged periods by pharmacologic antagonist or by denervation

Question 38

How do you overcome tachyphylaxsis?

Answer 38

- increase dose - change drug - drug holiday