04- Potency, Efficacy and Therapeutic Index

Question 1

pharmacodynamics

Answer 1

the study of how drugs interact in the human body

Question 2

true or false: all patient reacti the same to medications

Answer 2

false: Patient response to medications are highly individualized

Question 3

2 types of studies of pharmacodynamics

Answer 3

1. quantal effects

2. graded effects

Question 4

frequency distribution curve

Answer 4

a graphical representation of the number of patients responding to a drug action at different doses (quantal)

Question 5

dose-response curve

Answer 5

Plot of data showing effects of various doses of a toxic agent on a group of test organisms (graded)

Question 6

quantal effects use what type of patient questions

Answer 6

yes/no (ex. did drug reduce BP by 20mmhg?)

Question 7

do frequency distribution curves indicate magnitude/max effect of drug dose?

Answer 7

no.

Question 8

Median effective dose (ED50)

Answer 8

the dose of a drug that produces a therapeutic response in 50% (refered to as standard dose)

Question 9

therapeutic index

Answer 9

Ratio of a drug’s LD50 (or TD50) to its ED50

Question 10

median lethal dose (LD50)

Answer 10

The drug dose that causes death in 50 percent of the experimental animals in which it is tested.

Question 11

Median toxic dose (TD50)

Answer 11

The drug dose that produces a specific adverse (toxic) response in 50 percent of the patients in whom it is tested.

Question 12

quantal

Answer 12

saftey of a drug

LD50/ED50 = # client would have to increase dose #’s before seeing specific adverse effect on average

Question 13

ex. which drug is safer? a drug with a quantal number 4 for increased HR as the adverse effect or a quantal number of 2 with an adverse effect of increased resp.

Answer 13

drug A - up to 3x dose without adverse effect, on average

Question 14

why is the quantal number so important? which demographic?

Answer 14

elderly patient often forget and double dose. the higher the quantal number, the larger the therapeutic window, the safer the drug :)

Question 15

therapeutic window

Answer 15

Range based on minimum effective therapeutic [ ] and minimum toxic [ ] for specific toxic effect

Question 16

high alert medications are:

Answer 16

medications with very low therapeutic windows that effective and toxic dose ranges overlap

Question 17

true or false: approx. 40% of patients need higher drug doses to reach desired effects

Answer 17

false: 25%

Question 18

dose-response curve

Answer 18

Demonstrates magnitude of biological response to a drug

Obtained by observing and measuring patient responses at different doses of drug

Question 19

dose response curves are used to determine:

Answer 19

therapeutic range
efficacy
potency

Question 20

3 phases of dose response curve

Answer 20

1. few cells affected (not enough, little effect)
2. linear relationship between amount administered and degree of response
3. plateau - increasing dose has no effect (possible adverse)

Question 21

potency

Answer 21

Compares doses of 2+ drugs w respect to how much drug is needed to produce a specific response
usually based on median effective dose or concentration (ED50)

Question 22

efficacy

Answer 22

ability of drug to help client (exert more of a therapeutic response)

Question 23

what is a more important factor when assessing which drug is “better”: potency or efficacy

Answer 23

efficacy

Question 24

true or false: highly potent = lower affinity to receptor?

Answer 24

false

Question 25

association

Answer 25

drug binds to its receptor (k1 = Rate of drug-receptor complex formation)

Question 26

dissociation

Answer 26

k-1 = rate occurrence

Question 27

if k-1 is faster than k1 what does this mean in relation to association and dissociation and the drug’s affinity to a receptor?

Answer 27

association < dissociation

low affinity for receptor

Question 28

dissociation constant (Kd)

Answer 28

a measure of the affinity of the receptor for its ligand

k-1)/(k1

Question 29

true or false: a drug’s affinity for a receptor tells us how well drug binds to receptor and the action of the drug at the receptor

Answer 29

false: Doesn’t tell us anything about action of drug at receptor

Question 30

types of agonists:

Answer 30

Full, partial, inverse

Question 31

types of antagonists

Answer 31

reversible, competitive, non-competitive, and irreversible antagonists

Question 32

when do you use agonists vs. antagonists

Answer 32

agonist: if not making enough of ligand (replacement)
antagonist: too much of ligand or hormone

Question 33

Full agonist

Answer 33

Ability of a drug to produce 100% of the maximum response regardless of the potency
same effect as ligand (ex. dexamethasone for adrenal insufficiency)

Question 34

partial agonist

Answer 34

a drug that binds to a receptor and causes a response that is less than that caused by a full agonist (ex. aripiprazole for dopamine and management of bipolar or schizophrenia)

Question 35

true or false: efficacy of full agonist will always be higher than partial agonists

Answer 35

true

Question 36

inverse agonists

Answer 36

Bind to same receptor site as natural ligand, but induce opposite response to endogenous ligand (ex. GABA receptor. agonist have sedative response but inverse agonists have anxiogenic effects)

Question 37

when are inverse agonists viable?

Answer 37

Only occurs when receptors have an intrinsic (basal) level of activity

Question 38

true or false: inverse agonists have negative efficacy

Answer 38

true

Question 39

antagonist

Answer 39

bind to same receptor site ad endogenous ligand, but do not produce same effect (no efficacy)

Question 40

types of antagonists

Answer 40

reversible (competitive and non-competitive) and irreversible

Question 41

competitive agonist

Answer 41

Antagonist competes for same receptor binding site as endogenous ligand (linear drug response)

Question 42

non-competitive antagonist

Answer 42

binds to an allosteric (non-agonist) site on the receptor to prevent activation of the receptor

Question 43

clinical quality of non-competitive antagonists

Answer 43

poor. hard to predict response curve

Question 44

allosteric modulation

Answer 44

binding to another site on a receptor

Question 45

irreversible antagonist

Answer 45

A pharmacologic antagonist that cannot be overcome by increasing agonist concentration

Question 46

what does it mean for an irreversible antagonist to have its rate of dissociation (K-1) be 0?

Answer 46

Kd will be very low and its affinity to the receptor is very high

Question 47

ex. of irreversibel antagonists

Answer 47

biological weapons: Cholinesterase inhibitors (“nerve gases”)
drugs: Aspirin, omeprazole (management of GERD)